refactor(@ngtools/webpack): remove export of VirtualFileSystemDecorator type

This was only needed for the rollup loader.

Author: alan-agius4

packages/ngtools/webpack/src/index.ts

@@ -12,7 +12,4 @@ export { ngcLoader as default } from './loader';
 
 export const NgToolsLoader = __filename;
 
-// We shouldn't need to export this, but webpack-rollup-loader uses it.
-export type { VirtualFileSystemDecorator } from './virtual_file_system_decorator';
-
 export * as ivy from './ivy';