chore: Update discovery artifacts (#1410)

## Deleted keys were detected in the following stable discovery artifacts:
managedidentities v1 https://github.com/googleapis/google-api-python-client/commit/e96adbb1ba3e4e56d916cc28474f85543f17ad0e

## Discovery Artifact Change Summary:
feat(appengine): update the api https://github.com/googleapis/google-api-python-client/commit/ffcf86035a751e98a763c8a2d54b70d3a55ca14d
feat(containeranalysis): update the api https://github.com/googleapis/google-api-python-client/commit/9a1c70b7df3e074fc9fbd0eebdaf75a91046078c
feat(documentai): update the api https://github.com/googleapis/google-api-python-client/commit/07a6e774ac185442a99437896eaee774946b5846
feat(drive): update the api https://github.com/googleapis/google-api-python-client/commit/773910fdf25b084aa3623d24fe99c8a1330fbecb
feat(managedidentities): update the api https://github.com/googleapis/google-api-python-client/commit/e96adbb1ba3e4e56d916cc28474f85543f17ad0e
feat(spanner): update the api https://github.com/googleapis/google-api-python-client/commit/87da2f3605ec1b8986324cddc33f2b5601d3e896
diff --git a/docs/dyn/spanner_v1.projects.instances.html b/docs/dyn/spanner_v1.projects.instances.html
index 1e4d599..875fa51 100644
--- a/docs/dyn/spanner_v1.projects.instances.html
+++ b/docs/dyn/spanner_v1.projects.instances.html
@@ -156,6 +156,7 @@
     },
     "name": "A String", # Required. A unique identifier for the instance, which cannot be changed after the instance is created. Values are of the form `projects//instances/a-z*[a-z0-9]`. The final segment of the name must be between 2 and 64 characters in length.
     "nodeCount": 42, # The number of nodes allocated to this instance. This may be zero in API responses for instances that are not yet in state `READY`. See [the documentation](https://cloud.google.com/spanner/docs/instances#node_count) for more information about nodes.
+    "processingUnits": 42, # The number of processing units allocated to this instance. At most one of processing_units or node_count should be present in the message. This may be zero in API responses for instances that are not yet in state `READY`.
     "state": "A String", # Output only. The current instance state. For CreateInstance, the state must be either omitted or set to `CREATING`. For UpdateInstance, the state must be either omitted or set to `READY`.
   },
   "instanceId": "A String", # Required. The ID of the instance to create. Valid identifiers are of the form `a-z*[a-z0-9]` and must be between 2 and 64 characters in length.
@@ -234,6 +235,7 @@
   },
   "name": "A String", # Required. A unique identifier for the instance, which cannot be changed after the instance is created. Values are of the form `projects//instances/a-z*[a-z0-9]`. The final segment of the name must be between 2 and 64 characters in length.
   "nodeCount": 42, # The number of nodes allocated to this instance. This may be zero in API responses for instances that are not yet in state `READY`. See [the documentation](https://cloud.google.com/spanner/docs/instances#node_count) for more information about nodes.
+  "processingUnits": 42, # The number of processing units allocated to this instance. At most one of processing_units or node_count should be present in the message. This may be zero in API responses for instances that are not yet in state `READY`.
   "state": "A String", # Output only. The current instance state. For CreateInstance, the state must be either omitted or set to `CREATING`. For UpdateInstance, the state must be either omitted or set to `READY`.
 }</pre>
 </div>
@@ -312,6 +314,7 @@
       },
       &quot;name&quot;: &quot;A String&quot;, # Required. A unique identifier for the instance, which cannot be changed after the instance is created. Values are of the form `projects//instances/a-z*[a-z0-9]`. The final segment of the name must be between 2 and 64 characters in length.
       &quot;nodeCount&quot;: 42, # The number of nodes allocated to this instance. This may be zero in API responses for instances that are not yet in state `READY`. See [the documentation](https://cloud.google.com/spanner/docs/instances#node_count) for more information about nodes.
+      &quot;processingUnits&quot;: 42, # The number of processing units allocated to this instance. At most one of processing_units or node_count should be present in the message. This may be zero in API responses for instances that are not yet in state `READY`.
       &quot;state&quot;: &quot;A String&quot;, # Output only. The current instance state. For CreateInstance, the state must be either omitted or set to `CREATING`. For UpdateInstance, the state must be either omitted or set to `READY`.
     },
   ],
@@ -358,6 +361,7 @@
     },
     &quot;name&quot;: &quot;A String&quot;, # Required. A unique identifier for the instance, which cannot be changed after the instance is created. Values are of the form `projects//instances/a-z*[a-z0-9]`. The final segment of the name must be between 2 and 64 characters in length.
     &quot;nodeCount&quot;: 42, # The number of nodes allocated to this instance. This may be zero in API responses for instances that are not yet in state `READY`. See [the documentation](https://cloud.google.com/spanner/docs/instances#node_count) for more information about nodes.
+    &quot;processingUnits&quot;: 42, # The number of processing units allocated to this instance. At most one of processing_units or node_count should be present in the message. This may be zero in API responses for instances that are not yet in state `READY`.
     &quot;state&quot;: &quot;A String&quot;, # Output only. The current instance state. For CreateInstance, the state must be either omitted or set to `CREATING`. For UpdateInstance, the state must be either omitted or set to `READY`.
   },
 }