fix(core): remove core animation import symbols (#22692)

This patch removes the deprecated support for animation
symbol imports from @angular/core.

BREAKING CHANGE: it is no longer possible to import
animation-related functions from @angular/core. All
animation symbols must now be imported from @angular/animations.

PR Close #22692

aio/content/examples/router/src/app/animations.ts

@@ -1,8 +1,8 @@
 // #docregion
-import { animate, AnimationEntryMetadata, state, style, transition, trigger } from '@angular/core';
+import { animate, state, style, transition, trigger } from '@angular/animations';
 
 // Component transition animations
-export const slideInDownAnimation: AnimationEntryMetadata =
+export const slideInDownAnimation =
   trigger('routeAnimation', [
     state('*',
       style({