chore(deps): update dependency sinon to v9 (#531)

Author: renovate-bot

packages/google-cloud-node/package.json

@@ -69,7 +69,7 @@
     "null-loader": "^3.0.0",
     "pack-n-play": "^1.0.0-2",
     "prettier": "^1.13.5",
-    "sinon": "^8.0.0",
+    "sinon": "^9.0.0",
     "ts-loader": "^6.2.1",
     "typescript": "3.6.4",
     "webpack": "^4.41.2",