build(docs-infra): disable critical CSS inlining (#42435)

Previously, the critical CSS inlining optimization (which is turned on
by default in CLI v12+) was causing a Flash Of Unstyled Content (FOUC).
This was caused by the combination of the following facts:
- The way CSS inlining is implemented in the CLI makes loading the full
  styles asynchronous and non-render-blocking (so the app can bootstrap
  before the styles are fully downloaded).
- Angular.io does not employ the [app shell][1] pattern in order to
  render pages at build time, resulting in very minimal CSS rules being
  recognized as critical (for the purpose of inlining).

This commit fixes the FOUC by disabling the critical CSS inlining, while
we consider a better way to approach this (in order to be able to rip
the benefits of inlining without the FOUC).

[1]: https://angular.io/guide/app-shell

Fixes #42365

PR Close #42435

aio/angular.json

@@ -31,6 +31,14 @@
             "polyfills": "src/polyfills.ts",
             "tsConfig": "tsconfig.app.json",
             "webWorkerTsConfig": "tsconfig.worker.json",
+            "optimization": {
+              "fonts": true,
+              "scripts": true,
+              "styles": {
+                "inlineCritical": false,
+                "minify": true
+              }
+            },
             "outputHashing": "all",
             "sourceMap": true,
             "namedChunks": true,