build(docs-infra): upgrade webpack-cli to 3.1.2 (#26306)

This is necessary to avoid webpack/webpack#8082, when installing
dependencies without taking the lockfile into account (e.g. with
`yarn aio-use-local` - locally or on CI).

PR Close #26306

aio/package.json

@@ -155,7 +155,7 @@
     "unist-util-visit-parents": "^1.1.1",
     "vrsource-tslint-rules": "^5.8.2",
     "watchr": "^3.0.1",
-    "webpack-cli": "^2.0.14",
+    "webpack-cli": "^3.1.2",
     "xregexp": "^4.0.0",
     "yargs": "^7.0.2"
   }