chore(deps): update dependency fs-extra to v9 (#749)

Author: renovate-bot

packages/packages/google-gax/package.json

@@ -55,7 +55,7 @@
     "eslint-plugin-prettier": "^3.0.0",
     "execa": "^4.0.0",
     "file-loader": "^6.0.0",
-    "fs-extra": "^8.0.0",
+    "fs-extra": "^9.0.0",
     "google-proto-files": "^1.0.0",
     "gts": "^1.0.0",
     "is-docker": "^2.0.0",