[sheriff] Disable PasswordsSettingsTestCase.testManyPasswords on iPad.

PasswordsSettingsTestCase.testManyPasswords is failing on
(ipad 5th gen ios 11.4.1).
It failed on this assertion every time:
https://cs.chromium.org/chromium/src/ios/chrome/browser/ui/settings/passwords_settings_egtest.mm?rcl=e1d1f67d8f56f9f45b01db4d4f523dda21b05366&l=293

Not sure about the reason, cannot reproduce the failure locally.

Has filed a bug(crbug.com/906551) to track this.

TBR=noyau@chromium.org

Change-Id: I1a4d0bc62e5b16c7c3bad69b7587166ccd509bd8
Reviewed-on: https://chromium-review.googlesource.com/c/1341828
Commit-Queue: Yi Su <mrsuyi@chromium.org>
Reviewed-by: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609250}

ios/chrome/browser/ui/settings/passwords_settings_egtest.mm

@@ -1431,6 +1431,11 @@ PasswordForm CreateSampleFormWithIndex(int index) {
 // any device. To limit the effect of (2), custom large scrolling steps are
 // added to the usual scrolling actions.
 - (void)testManyPasswords {
+  if (IsIPadIdiom()) {
+    // TODO(crbug.com/906551): Enable the test on iPad once the bug is fixed.
+    EARL_GREY_TEST_DISABLED(@"Disabled for iPad.");
+  }
+
   // Enough just to ensure filling more than one page on all devices.
   constexpr int kPasswordsCount = 15;