fix(deps): update dependency @google-cloud/common to v4 (#793)

Author: renovate-bot

package.json

@@ -47,7 +47,7 @@
     "precompile": "gts clean"
   },
   "dependencies": {
-    "@google-cloud/common": "^3.0.0",
+    "@google-cloud/common": "^4.0.0",
     "@google-cloud/promisify": "^2.0.0",
     "arrify": "^2.0.0",
     "extend": "^3.0.2",