fix(deps): update dependency through2 to v3 (#295)

Author: renovate[bot]

core/common/package.json

@@ -71,7 +71,7 @@
     "google-auth-library": "^2.0.0",
     "pify": "^4.0.0",
     "retry-request": "^4.0.0",
-    "through2": "^2.0.3"
+    "through2": "^3.0.0"
   },
   "devDependencies": {
     "@google-cloud/nodejs-repo-tools": "^2.3.3",