[iOS] Re-enable testPostFormToSamePage on device

The tests were marked as flaky but I can't repro.
Re-enabling them.

Fixed: 714303
Change-Id: If329171730bd10aa4a6ed9ed9c7458b10f3587e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2213531Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#772582}

ios/chrome/browser/web/forms_egtest.mm

@@ -498,13 +498,7 @@ id<GREYMatcher> ResendPostButtonMatcher() {
 // Tests that pressing the button on a POST-based form with same-page action
 // does not change the page URL and that the back button works as expected
 // afterwards.
-// TODO(crbug.com/714303): Re-enable this test on devices.
-#if TARGET_IPHONE_SIMULATOR
-#define MAYBE_testPostFormToSamePage testPostFormToSamePage
-#else
-#define MAYBE_testPostFormToSamePage FLAKY_testPostFormToSamePage
-#endif
-- (void)MAYBE_testPostFormToSamePage {
+- (void)testPostFormToSamePage {
   web::test::SetUpHttpServer(std::make_unique<TestFormResponseProvider>());
   const GURL formURL = GetFormPostOnSamePageUrl();