build: remove main() from specs (#21053)

PR Close #21053

packages/compiler/test/config_spec.ts

@@ -9,7 +9,7 @@
 import {MissingTranslationStrategy} from '@angular/core';
 import {CompilerConfig} from '../src/config';
 
-export function main() {
+{
   describe('compiler config', () => {
     it('should set missing translation strategy', () => {
       const config = new CompilerConfig({missingTranslation: MissingTranslationStrategy.Error});