refactor(cdk/a11y): un-deprecate focus trap (#28768)

The `FocusTrap` and `FocusTrapFactory` symbols were marked as deprecated a while ago, but the only way to provide the `ConfigurableFocusTrap` is to reference the deprecated symbols. These changes un-deprecate the former to avoid confusion.

(cherry picked from commit 70d416f)

src/cdk/a11y/focus-trap/focus-trap.ts

@@ -32,9 +32,6 @@ import {InteractivityChecker} from '../interactivity-checker/interactivity-check
  * This class currently uses a relatively simple approach to focus trapping.
  * It assumes that the tab order is the same as DOM order, which is not necessarily true.
  * Things like `tabIndex > 0`, flex `order`, and shadow roots can cause the two to be misaligned.
- *
- * @deprecated Use `ConfigurableFocusTrap` instead.
- * @breaking-change 11.0.0
  */
 export class FocusTrap {
   private _startAnchor: HTMLElement | null;
@@ -368,8 +365,6 @@ export class FocusTrap {
 
 /**
  * Factory that allows easy instantiation of focus traps.
- * @deprecated Use `ConfigurableFocusTrapFactory` instead.
- * @breaking-change 11.0.0
  */
 @Injectable({providedIn: 'root'})
 export class FocusTrapFactory {

tools/public_api_guard/cdk/a11y.md

@@ -217,7 +217,7 @@ export { FocusOptions_2 as FocusOptions }
 // @public (undocumented)
 export type FocusOrigin = 'touch' | 'mouse' | 'keyboard' | 'program' | null;
 
-// @public @deprecated
+// @public
 export class FocusTrap {
     constructor(_element: HTMLElement, _checker: InteractivityChecker, _ngZone: NgZone, _document: Document, deferAnchors?: boolean);
     attachAnchors(): boolean;
@@ -246,7 +246,7 @@ export class FocusTrap {
     protected toggleAnchors(enabled: boolean): void;
 }
 
-// @public @deprecated
+// @public
 export class FocusTrapFactory {
     constructor(_checker: InteractivityChecker, _ngZone: NgZone, _document: any);
     create(element: HTMLElement, deferCaptureElements?: boolean): FocusTrap;