Remove html_config from document_register_basic_test

Change-Id: I9df37df1d6f4d0ad90d33e09e6da4b94fb668fa2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/138387
Commit-Queue: Srujan Gaddam <[email protected]>
Reviewed-by: Bob Nystrom <[email protected]>

Author: srujzs

tests/lib_2/html/custom/document_register_basic_test.dart

@@ -7,7 +7,6 @@ library document_register_basic_test;
 import 'dart:html';
 
 import 'package:unittest/unittest.dart';
-import 'package:unittest/html_config.dart';
 
 import 'utils.dart';
 
@@ -42,8 +41,6 @@ abstract class BadC extends HtmlElement {
 }
 
 main() {
-  useHtmlConfiguration();
-
   // Adapted from Blink's fast/dom/custom/document-register-basic test.
 
   setUp(() => customElementsReady);