fix: upgrade to @google-cloud/common@0.20.3 (#158)

Fixes: googleapis/nodejs-error-reporting#155

Author: ofrobots

handwritten/package-lock.json

@@ -54,7 +54,7 @@
     "license-check": "jsgl --local ."
   },
   "dependencies": {
-    "@google-cloud/common": "^0.20.0",
+    "@google-cloud/common": "^0.20.3",
     "is": "^3.2.1",
     "lodash.has": "^4.5.2"
   },