docs: remove all deprecated @stable jsdoc tags (#23210)

These are no longer needed as stable docs are computed as those that
do not have `@experimental` or `@deprecated` tags.

PR Close #23210

packages/core/testing/src/async.ts

@@ -23,7 +23,7 @@ import {asyncFallback} from './async_fallback';
  * });
  * ```
  *
- * @stable
+ *
  */
 export function async(fn: Function): (done: any) => any {
   const _Zone: any = typeof Zone !== 'undefined' ? Zone : null;

packages/core/testing/src/async_fallback.ts

@@ -29,7 +29,7 @@ const _global = <any>(typeof window === 'undefined' ? global : window);
  * });
  * ```
  *
- * @stable
+ *
  */
 export function asyncFallback(fn: Function): (done: any) => any {
   // If we're running using the Jasmine test framework, adapt to call the 'done'

packages/core/testing/src/component_fixture.ts

@@ -12,7 +12,7 @@ import {ChangeDetectorRef, ComponentRef, DebugElement, ElementRef, NgZone, Rende
 /**
  * Fixture for debugging and testing a component.
  *
- * @stable
+ *
  */
 export class ComponentFixture<T> {
   /**

packages/core/testing/src/test_bed.ts

@@ -55,7 +55,7 @@ export type TestModuleMetadata = {
  *
  * TestBed is the primary api for writing unit tests for Angular applications and libraries.
  *
- * @stable
+ *
  */
 export class TestBed implements Injector {
   /**
@@ -606,7 +606,7 @@ export function getTestBed() {
  * eventually
  *   becomes `it('...', @Inject (object: AClass, async: AsyncTestCompleter) => { ... });`
  *
- * @stable
+ *
  */
 export function inject(tokens: any[], fn: Function): () => any {
   const testBed = getTestBed();