Disable ClipboardHistoryWithMultiProfileBrowserTest.ShouldPasteHistoryAsPlainText

It's flaky as far as flakiness dashboard history goes.
Recently introduced in https://chromium-review.googlesource.com/c/chromium/src/+/2348294
assigning as such.

TBR=dmblack@google.com, xiyuan@chromium.org

Bug: 1123542
Change-Id: I8195565f33e6637401a77326513f551c17ca4661
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2385755Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803138}

chrome/browser/ui/ash/clipboard_history_browsertest.cc

@@ -353,8 +353,9 @@ IN_PROC_BROWSER_TEST_F(ClipboardHistoryWithMultiProfileBrowserTest,
   Release(ui::KeyboardCode::VKEY_COMMAND);
 }
 
+// Flaky: crbug.com/1123542
 IN_PROC_BROWSER_TEST_F(ClipboardHistoryWithMultiProfileBrowserTest,
-                       ShouldPasteHistoryAsPlainText) {
+                       DISABLED_ShouldPasteHistoryAsPlainText) {
   LoginUser(account_id1_);
 
   // Create a browser and cache its active web contents.