feat(router-store): remove deprecated getSelectors method (#3816)

Closes #3815 

BREAKING CHANGES:

The deprecated `getSelectors` function has been removed from the `@ngrx/router-store` package.

BEFORE:

The @ngrx/router-store package exports the `getSelectors` function. 

AFTER:

The @ngrx/router-store package no longer exports the `getSelectors` function. A migration has been provided to replace existing usage

modules/router-store/src/index.ts

@@ -44,9 +44,5 @@ export {
   MinimalRouterStateSnapshot,
   MinimalRouterStateSerializer,
 } from './serializers/minimal_serializer';
-export {
-  getRouterSelectors,
-  getSelectors,
-  createRouterSelector,
-} from './router_selectors';
+export { getRouterSelectors, createRouterSelector } from './router_selectors';
 export { provideRouterStore } from './provide_router_store';

modules/router-store/src/router_selectors.ts

@@ -13,12 +13,6 @@ export function createRouterSelector<
   return createFeatureSelector(DEFAULT_ROUTER_FEATURENAME);
 }
 
-/**
- * @deprecated This function is deprecated in favor of `getRouterSelectors`.
- * For more info see: https://github.com/ngrx/platform/issues/3738
- */
-export const getSelectors = getRouterSelectors;
-
 export function getRouterSelectors<V extends Record<string, any>>(
   selectState: (state: V) => RouterReducerState<any> = createRouterSelector<V>()
 ): RouterStateSelectors<V> {