Update cosmos-db.json (#16052)

Added viewDefinition as required property

Author: ajparule

specification/cosmos-db/resource-manager/Microsoft.DocumentDB/preview/2021-07-01-preview/cosmos-db.json

@@ -8598,7 +8598,8 @@
         }
       },
       "required": [
-        "id"
+        "id",
+        "viewDefinition"
       ]
     },
     "CreateUpdateOptions": {