chore: Update discovery artifacts (#1379)

## Deleted keys were detected in the following stable discovery artifacts:
servicemanagement v1 https://github.com/googleapis/google-api-python-client/commit/ac046117b12b43e03e748ebd0c442b340ed99183

## Discovery Artifact Change Summary:
feat(adexchangebuyer2): update the api https://github.com/googleapis/google-api-python-client/commit/e1ebe49bc9e2e007c61188202f0345c96083c19a
feat(displayvideo): update the api https://github.com/googleapis/google-api-python-client/commit/4f37d8b0d43f2172fdae627605947b3ba15b06c2
feat(gkehub): update the api https://github.com/googleapis/google-api-python-client/commit/e12ff0958ed9016356c8711039a15334d2f0d6f6
feat(servicemanagement): update the api https://github.com/googleapis/google-api-python-client/commit/ac046117b12b43e03e748ebd0c442b340ed99183
feat(spanner): update the api https://github.com/googleapis/google-api-python-client/commit/43f1be2ea175a79e463d77cf3155e7b8ab1b26f6
diff --git a/googleapiclient/discovery_cache/documents/content.v2.json b/googleapiclient/discovery_cache/documents/content.v2.json
index d220b4f..62d1f06 100644
--- a/googleapiclient/discovery_cache/documents/content.v2.json
+++ b/googleapiclient/discovery_cache/documents/content.v2.json
@@ -3298,7 +3298,7 @@
       }
     }
   },
-  "revision": "20210514",
+  "revision": "20210519",
   "rootUrl": "https://shoppingcontent.googleapis.com/",
   "schemas": {
     "Account": {
@@ -10313,7 +10313,7 @@
           "type": "string"
         },
         "value": {
-          "description": "Required. The weight represented as a number.",
+          "description": "Required. The weight represented as a number. The weight can have a maximum precision of four decimal places.",
           "type": "string"
         }
       },