upgrade GRPC to 1.16.0 in testing

Author: squirly

packages/testing/package.json

@@ -19,7 +19,7 @@
     "@firebase/logger": "0.1.1",
     "@firebase/util": "0.2.2",
     "@types/request": "2.47.1",
-    "grpc": "1.13.1",
+    "grpc": "1.16.0",
     "request": "2.88.0"
   },
   "devDependencies": {