Fix code for disabling test

The condition for disabling the test was wrong, the test is failing on
device.

Bug: 855368
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I6b3a5696e6cdec5b80e12bc3b74d81c443f8cd46
Reviewed-on: https://chromium-review.googlesource.com/1113186Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569991}

ios/chrome/browser/ui/fullscreen/fullscreen_egtest.mm

@@ -427,7 +427,7 @@ void AssertURLIs(const GURL& expectedURL) {
 // Tests that the header is shown when loading an error page in a native view
 // even if fullscreen was enabled previously.
 - (void)testShowHeaderOnErrorPage {
-#if TARGET_OS_SIMULATOR
+#if !TARGET_OS_SIMULATOR
   if (!base::ios::IsRunningOnIOS11OrLater()) {
     // TODO(crbug.com/855368): Reenable this test.
     EARL_GREY_TEST_DISABLED(@"Test failing on iOS 10 devices");