refactor(@ngtools/webpack): remove deprecated ivy namespace

BREAKING CHANGE:

`ivy` namespace has been removed from the public API.

- `ivy.AngularWebpackPlugin` -> `AngularWebpackPlugin`
- `ivy.AngularPluginOptions` -> `AngularPluginOptions`

Author: alan-agius4

src/index.ts

@@ -6,22 +6,9 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import * as ivyInternal from './ivy';
-
 export {
   AngularWebpackLoaderPath,
   AngularWebpackPlugin,
   AngularWebpackPluginOptions,
   default,
 } from './ivy';
-
-/** @deprecated Deprecated as of v12, please use the direct exports
- * (`AngularWebpackPlugin` instead of `ivy.AngularWebpackPlugin`)
- */
-// eslint-disable-next-line @typescript-eslint/no-namespace
-export namespace ivy {
-  export const AngularWebpackLoaderPath = ivyInternal.AngularWebpackLoaderPath;
-  export const AngularWebpackPlugin = ivyInternal.AngularWebpackPlugin;
-  export type AngularWebpackPlugin = ivyInternal.AngularWebpackPlugin;
-  export type AngularPluginOptions = ivyInternal.AngularWebpackPluginOptions;
-}