chore: Update discovery artifacts (#1375)

## Deleted keys were detected in the following stable discovery artifacts:
servicenetworking v1 https://github.com/googleapis/google-api-python-client/commit/c0ad756013c602597e477bc0e22e7b2771689214

## Deleted keys were detected in the following pre-stable discovery artifacts:
retail v2alpha https://github.com/googleapis/google-api-python-client/commit/c9d7a149295d827110c789e464b4f97edc13cbaa
servicenetworking v1beta https://github.com/googleapis/google-api-python-client/commit/c0ad756013c602597e477bc0e22e7b2771689214

## Discovery Artifact Change Summary:
feat(composer): update the api https://github.com/googleapis/google-api-python-client/commit/c2cb2746320fa7b6c1536028794f53576c0f1ddd
feat(compute): update the api https://github.com/googleapis/google-api-python-client/commit/2cdcd0a21223a229e711778a3cf1b38c63521d96
feat(dfareporting): update the api https://github.com/googleapis/google-api-python-client/commit/73f7d790e1585322547fe7cb39c8f36e7b400121
feat(dialogflow): update the api https://github.com/googleapis/google-api-python-client/commit/8edd852f294eaccfa6a0e7288d54a2d751f53506
feat(retail): update the api https://github.com/googleapis/google-api-python-client/commit/c9d7a149295d827110c789e464b4f97edc13cbaa
feat(sasportal): update the api https://github.com/googleapis/google-api-python-client/commit/12683cabbf8deaf0a884147b98c30345786874a6
feat(servicenetworking): update the api https://github.com/googleapis/google-api-python-client/commit/c0ad756013c602597e477bc0e22e7b2771689214
diff --git a/googleapiclient/discovery_cache/documents/translate.v3.json b/googleapiclient/discovery_cache/documents/translate.v3.json
index 4b5a327..2a337a1 100644
--- a/googleapiclient/discovery_cache/documents/translate.v3.json
+++ b/googleapiclient/discovery_cache/documents/translate.v3.json
@@ -687,7 +687,7 @@
       }
     }
   },
-  "revision": "20210513",
+  "revision": "20210521",
   "rootUrl": "https://translation.googleapis.com/",
   "schemas": {
     "BatchTranslateTextRequest": {
@@ -1217,7 +1217,7 @@
           "type": "string"
         },
         "translatedText": {
-          "description": "Text translated into the target language.",
+          "description": "Text translated into the target language. If an error occurs during translation, this field might be excluded from the response.",
           "type": "string"
         }
       },