Revert "[iOS] Re-enable testShowJavaScriptAfterNewTabAnimation"

This reverts commit 0a966f3c.

Reason for revert: Test is failing flakily.
Not due to crbug.com/989550 though.

Original change's description:
> [iOS] Re-enable testShowJavaScriptAfterNewTabAnimation
> 
> This test passes now after crrev.com/c/1769082, but we've noticed some
> flake that isn't reproducing.  This CL re-enables it separately so it
> can be easily reverted if necessary.
> 
> Bug: 989550
> Change-Id: If84c590547a57403ad0bd36079550fe98fc53b1a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1769354
> Auto-Submit: Kurt Horimoto <kkhorimoto@chromium.org>
> Reviewed-by: Justin Cohen <justincohen@chromium.org>
> Commit-Queue: Kurt Horimoto <kkhorimoto@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#691016}

TBR=justincohen@chromium.org,kkhorimoto@chromium.org

Change-Id: I20261d338b46862d68744461bdbc18ea3576d92b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 989550
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1775198Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Commit-Queue: Kurt Horimoto <kkhorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691297}

ios/chrome/browser/ui/dialogs/javascript_dialog_egtest.mm

@@ -575,6 +575,11 @@ void TapSuppressDialogsButton() {
 
 // Tests that an alert is presented after a new tab animation is finished.
 - (void)testShowJavaScriptAfterNewTabAnimation {
+  // TODO(crbug.com/989550) Disable broken context menu tests on Xc11b5.
+  if (@available(iOS 13, *)) {
+    EARL_GREY_TEST_DISABLED(@"Test disabled on iOS13.");
+  }
+
   // Load the test page with a link to kOnLoadAlertURL and long tap on the link.
   [self loadPageWithLink];