chore: Update discovery artifacts (#1374)

## Discovery Artifact Change Summary:
feat(gkehub): update the api https://github.com/googleapis/google-api-python-client/commit/b2c1bb00a3b41e9cdfe925dd90aa4bc677a55e33
feat(servicedirectory): update the api https://github.com/googleapis/google-api-python-client/commit/1a87cd4c32ff6145efb48dcbf12e644da1533f0b
feat(servicenetworking): update the api https://github.com/googleapis/google-api-python-client/commit/12d70c78040997c7354bcf66a0afe6b428d493d6
diff --git a/googleapiclient/discovery_cache/documents/servicenetworking.v1beta.json b/googleapiclient/discovery_cache/documents/servicenetworking.v1beta.json
index c5e455c..5ab86e0 100644
--- a/googleapiclient/discovery_cache/documents/servicenetworking.v1beta.json
+++ b/googleapiclient/discovery_cache/documents/servicenetworking.v1beta.json
@@ -307,7 +307,7 @@
       }
     }
   },
-  "revision": "20210517",
+  "revision": "20210519",
   "rootUrl": "https://servicenetworking.googleapis.com/",
   "schemas": {
     "AddDnsRecordSetMetadata": {
@@ -1826,6 +1826,12 @@
       },
       "type": "object"
     },
+    "PartialDeleteConnectionMetadata": {
+      "description": "Metadata provided through GetOperation request for the LRO generated by Partial Delete Connection API",
+      "id": "PartialDeleteConnectionMetadata",
+      "properties": {},
+      "type": "object"
+    },
     "PeeredDnsDomain": {
       "description": "DNS domain suffix for which requests originating in the producer VPC network are resolved in the associated consumer VPC network.",
       "id": "PeeredDnsDomain",