Re-enabling flaky fullscreen test to see failure log

No-Try: True
Bug: 1123907
Change-Id: I5faf2a3bde9610df72062a888cb40c157a6ec623
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2505913Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: Shengfa Lin <shengfa@google.com>
Cr-Commit-Position: refs/heads/master@{#821734}

third_party/blink/web_tests/WebDriverExpectations

@@ -236,7 +236,6 @@ crbug.com/1065297 [ Linux ] external/wpt/webdriver/tests/perform_actions/pointer
 crbug.com/1065297 [ Linux ] external/wpt/webdriver/tests/perform_actions/pointer.py>>test_drag_and_drop_with_draggable_element[0] [ Failure ]
 crbug.com/1065297 [ Linux ] external/wpt/webdriver/tests/perform_actions/pointer.py>>test_drag_and_drop_with_draggable_element[300] [ Failure ]
 crbug.com/1065297 [ Linux ] external/wpt/webdriver/tests/perform_actions/key_shortcuts.py>>test_mod_a_mod_c_right_mod_v_pastes_text [ Failure ]
-crbug.com/1123907 [ Linux ] external/wpt/webdriver/tests/fullscreen_window/fullscreen.py>>test_fullscreen_twice_is_idempotent [ Failure Pass ]
 crbug.com/1123907 [ Linux ] external/wpt/webdriver/tests/fullscreen_window/stress.py>>test_stress[2] [ Failure Pass ]
 crbug.com/1123907 [ Linux ] external/wpt/webdriver/tests/fullscreen_window/stress.py>>test_stress[3] [ Failure Pass ]
 crbug.com/1123907 [ Linux ] external/wpt/webdriver/tests/fullscreen_window/stress.py>>test_stress[4] [ Failure Pass ]