feat(servicecontrol): update the API

#### servicecontrol:v1
The following keys were added:
- schemas.Operation.properties.extensions.description
- schemas.Operation.properties.extensions.items.additionalProperties.description
- schemas.Operation.properties.extensions.items.additionalProperties.type
- schemas.Operation.properties.extensions.items.type
- schemas.Operation.properties.extensions.type

discovery/servicecontrol-v1.json

@@ -197,7 +197,7 @@
       }
     }
   },
-  "revision": "20200601",
+  "revision": "20200703",
   "rootUrl": "https://servicecontrol.googleapis.com/",
   "schemas": {
     "AllocateInfo": {
@@ -1165,6 +1165,17 @@
           "format": "google-datetime",
           "type": "string"
         },
+        "extensions": {
+          "description": "Unimplemented.",
+          "items": {
+            "additionalProperties": {
+              "description": "Properties of the object. Contains field @type with type URL.",
+              "type": "any"
+            },
+            "type": "object"
+          },
+          "type": "array"
+        },
         "importance": {
           "description": "DO NOT USE. This is an experimental field.",
           "enum": [

src/apis/servicecontrol/v1.ts

@@ -795,6 +795,10 @@ export namespace servicecontrol_v1 {
      * End time of the operation. Required when the operation is used in ServiceController.Report, but optional when the operation is used in ServiceController.Check.
      */
     endTime?: string | null;
+    /**
+     * Unimplemented.
+     */
+    extensions?: Array<{[key: string]: any}> | null;
     /**
      * DO NOT USE. This is an experimental field.
      */