Removed deprecated testing dependency

[cdavalos7]

Motivation for features / changes

@angular/platform-browser-dynamic/testing was deprecated in Angular 21. The
OSS build still accepts it, but the internal build no longer does, so it has to
go.

The internal build also reported a strictDeps error on initialize_testbed.ts:

`error TS2307: [strictDeps] transitive dependency on .../core/index.d.ts
not allowed. Please add the BUILD target to your rule's deps.`

Technical description of changes

1. testing/initialize_testbed.ts: removed the 2 deprecated symbols for their @angular/platform-browser/testing equivalents, dropped dynamic from platformBrowserDynamicTesting and BrowserDynamicTestingModule.
2. angular/BUILD: rename expect_angular_platform_browser_dynamic_testing expect_angular_platform_browser_testing, now pointing at @npm//@angular/platform-browser. Its four consumer BUILD files were updated to match.
3. testing/BUILD: add @npm//@angular/core to initialize_testbed, which is the strictDeps fix.

Some references were removed rather than renamed, because they were not used:

4. settings/_views/settings_test.ts andapp_routing/views/router_outlet_test.ts imported BrowserDynamicTestingModule without ever using it, so the import lines were removed.
5. integration_test_module in testing/BUILD declared the dependency although none of its sources import the package.