chore(deps): update dependency webpack-cli to v6 (#141)

Co-authored-by: miguel <miguelvelezsa@google.com>

Author: renovate-bot

packages/gaxios/system-test/fixtures/sample/package.json

@@ -24,6 +24,6 @@
     "ts-loader": "^8.0.0",
     "typescript": "^5.0.0",
     "webpack": "^5.35.0",
-    "webpack-cli": "^4.0.0"
+    "webpack-cli": "^6.0.0"
   }
 }