[web] Re-enable history tests on Safari (#41901)

Fixes flutter/flutter#51169

lib/web_ui/test/engine/history_test.dart

@@ -2,10 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// TODO(mdebbar): https://github.com/flutter/flutter/issues/51169
-@TestOn('!safari')
-library;
-
 import 'dart:async';
 import 'dart:js_interop'
     show JSExportedDartFunction, JSExportedDartFunctionToFunction;
@@ -14,7 +10,6 @@ import 'package:quiver/testing/async.dart';
 import 'package:test/bootstrap/browser.dart';
 import 'package:test/test.dart';
 import 'package:ui/src/engine.dart' show window;
-import 'package:ui/src/engine/browser_detection.dart';
 import 'package:ui/src/engine/dom.dart'
     show DomEvent, DomEventListener, createDomPopStateEvent;
 import 'package:ui/src/engine/navigation.dart';
@@ -285,7 +280,7 @@ void testMain() {
       // 3. The active entry doesn't belong to our history anymore because we
       // navigated past it.
       expect(originalStrategy.currentEntryIndex, -1);
-    }, skip: browserEngine == BrowserEngine.webkit);
+    });
 
     test('handle user-provided url', () async {
       final TestUrlStrategy strategy = TestUrlStrategy.fromEntry(
@@ -522,7 +517,7 @@ void testMain() {
       expect(strategy.currentEntryIndex, 0);
       expect(strategy.currentEntry.state, _tagStateWithSerialCount('initial state', 0));
       expect(strategy.currentEntry.url, '/home');
-    }, skip: browserEngine == BrowserEngine.webkit);
+    });
 
     test('handle user-provided url', () async {
       final TestUrlStrategy strategy = TestUrlStrategy.fromEntry(