fix(material/snack-bar): remove deprecated animation definitions

Deletes publicly-exported animation definitions that were marked for removal in v21.

BREAKING CHANGE:
* `matSnackBarAnimations` symbol has been removed.

Author: crisbeto

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

@@ -76,11 +76,6 @@ export class MatSnackBarActions {
     static ɵfac: i0.ɵɵFactoryDeclaration<MatSnackBarActions, never>;
 }
 
-// @public @deprecated
-export const matSnackBarAnimations: {
-    readonly snackBarState: any;
-};
-
 // @public
 export class MatSnackBarConfig<D = any> {
     announcementMessage?: string;

src/material/snack-bar/BUILD.bazel

@@ -74,7 +74,6 @@ ng_project(
         "public-api.ts",
         "simple-snack-bar.ts",
         "snack-bar.ts",
-        "snack-bar-animations.ts",
         "snack-bar-config.ts",
         "snack-bar-container.ts",
         "snack-bar-content.ts",

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

@@ -13,4 +13,3 @@ export * from './snack-bar';
 export * from './snack-bar-module';
 export * from './snack-bar-config';
 export * from './snack-bar-ref';
-export * from './snack-bar-animations';