chore(deps): update dependency sinon to v12 (#222)

Author: renovate-bot

packages/google-cloud-aiplatform/package.json

@@ -63,7 +63,7 @@
     "mocha": "^8.2.1",
     "null-loader": "^4.0.1",
     "pack-n-play": "^1.0.0-2",
-    "sinon": "^11.0.0",
+    "sinon": "^12.0.0",
     "ts-loader": "^9.0.0",
     "typescript": "^4.0.5",
     "webpack": "^5.4.0",