fix(material/snack-bar): remove deprecated factory functions

Removes factory functions that we had marked as deprecated for v21. These functions aren't necessary since we switched to standalone.

BREAKING CHANGE:
* `MAT_SNACK_BAR_DEFAULT_OPTIONS_FACTORY` has been removed.

Author: crisbeto

goldens/material/snack-bar/index.api.md

@@ -37,9 +37,6 @@ export const MAT_SNACK_BAR_DATA: InjectionToken<any>;
 // @public
 export const MAT_SNACK_BAR_DEFAULT_OPTIONS: InjectionToken<MatSnackBarConfig<any>>;
 
-// @public @deprecated
-export function MAT_SNACK_BAR_DEFAULT_OPTIONS_FACTORY(): MatSnackBarConfig;
-
 // @public
 export class MatSnackBar implements OnDestroy {
     constructor(...args: unknown[]);

src/material/snack-bar/snack-bar.ts

@@ -33,21 +33,12 @@ import {ComponentPortal, TemplatePortal} from '@angular/cdk/portal';
 import {takeUntil} from 'rxjs/operators';
 import {_animationsDisabled} from '../core';
 
-/**
- * @docs-private
- * @deprecated No longer used, will be removed.
- * @breaking-change 21.0.0
- */
-export function MAT_SNACK_BAR_DEFAULT_OPTIONS_FACTORY(): MatSnackBarConfig {
-  return new MatSnackBarConfig();
-}
-
 /** Injection token that can be used to specify default snack bar. */
 export const MAT_SNACK_BAR_DEFAULT_OPTIONS = new InjectionToken<MatSnackBarConfig>(
   'mat-snack-bar-default-options',
   {
     providedIn: 'root',
-    factory: MAT_SNACK_BAR_DEFAULT_OPTIONS_FACTORY,
+    factory: () => new MatSnackBarConfig(),
   },
 );