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/common/http/testing/src/backend.ts

@@ -23,7 +23,7 @@ import {TestRequest} from './request';
  * requests were made and then flush them. In the end, a verify() method asserts
  * that no unexpected requests were made.
  *
- * @stable
+ *
  */
 @Injectable()
 export class HttpClientTestingBackend implements HttpBackend, HttpTestingController {