chore: remove angular_entry point (#8975)

this is obsolete and no longer needed. it wasn't part of the public api so it's ok to remove.

modules/@angular/core/src/angular_entrypoint.dart

@@ -1,23 +0,0 @@
-library angular2.src.core.angular_entrypoint;
-
-/**
- * Marks a function or method as an Angular 2 entrypoint. Only necessary in Dart code.
- *
- * The optional `name` parameter will be reflected in logs when the entry point is processed.
- *
- * See [the wiki][] for detailed documentation.
- * [the wiki]: https://github.com/angular/angular/wiki/Angular-2-Dart-Transformer#entry_points
- *
- * ## Example
- *
- * ```
- * @AngularEntrypoint("name-for-debug")
- * void main() {
- *   bootstrap(MyComponent);
- * }
- * ```
- */
-class AngularEntrypoint {
-  final String name;
-  const AngularEntrypoint([this.name]);
-}

modules/@angular/core/src/angular_entrypoint.ts

@@ -1,3 +0,0 @@
-import 'angular2/src/facade/lang';  // kept so that Tools know this is an ES6 file
-
-// TS does not have AngularEntrypoint