build(docs-infra): remove unneeded allowEmptyCodegenFiles option in Ivy mode (#30911)

Previously, when switching to Ivy mode (e.g. to run tests on CI), we had
to add `allowEmptyCodegenFiles: true` to the `angularCompilerOptions` in
`tsconfig.app.json`.

This isn't necessary any more (potentially since we switched to dynamic
imports for loading lazy modules in #30704), so this commit removes it
from the `switch-to-ivy.js` script.

PR Close #30911

aio/scripts/switch-to-ivy.js

@@ -13,8 +13,6 @@ const ROOT_DIR = resolve(__dirname, '..');
 const NG_JSON = join(ROOT_DIR, 'angular.json');
 const NG_COMPILER_OPTS = {
   angularCompilerOptions: {
-    // Related Jira issue: FW-737
-    allowEmptyCodegenFiles: true,
     enableIvy: true,
   },
 };