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

PR Close #21053

packages/forms/test/form_array_spec.ts

@@ -12,7 +12,7 @@ import {AbstractControl, FormArray, FormControl, FormGroup, ValidationErrors} fr
 import {of } from 'rxjs/observable/of';
 import {Validators} from '../src/validators';
 
-export function main() {
+(function(){
   function asyncValidator(expected: string, timeouts = {}) {
     return (c: AbstractControl) => {
       let resolve: (result: any) => void = undefined !;
@@ -1100,4 +1100,4 @@ export function main() {
 
     });
   });
-}
+})();