Disable flaky TabGridDialogTest#testAccessibilityString

TBR=wychen

Bug: 1128345
Change-Id: I8acacd7a065cccd5895f14b8185e88d50dc2644f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2414839Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807627}

chrome/android/features/tab_ui/javatests/src/org/chromium/chrome/browser/tasks/tab_management/TabGridDialogTest.java

@@ -795,6 +795,7 @@ public class TabGridDialogTest {
 
     @Test
     @MediumTest
+    @DisabledTest(message = "TODO(crbug.com/1128345): Fix flakiness.")
     // clang-format off
     @Features.EnableFeatures({ChromeFeatureList.TAB_GROUPS_CONTINUATION_ANDROID,
             ChromeFeatureList.TAB_GRID_LAYOUT_ANDROID + "<Study"})