Remove uses of unittest in the HTML tests where possible.

pkg/dev_compiler/test/codegen/lib/html/range_test.dart

-library range_test;
+import 'dart:html';
 
-import 'dart:html';
-import 'package:unittest/unittest.dart';
-import 'package:unittest/html_individual_config.dart';
+import 'package:expect/minitest.dart';
 
 main() {
-  useHtmlIndividualConfiguration();
-
   group('supported', () {
     test('supports_createContextualFragment', () {
       expect(Range.supportsCreateContextualFragment, isTrue);
     });
   });
 
   group('functional', () {
     test('supported works', () {
       var range = new Range();
       range.selectNode(document.body);
 
       var expectation = Range.supportsCreateContextualFragment ?
           returnsNormally : throws;
 
       expect(() {
         range.createContextualFragment('<div></div>');
       }, expectation);
     });
   });
 }