[CleanUp] Enable test on Mac.

Enables a virtual test for mouse-interactions-dsf-2.html on Mac.

Bug: 1009892
Change-Id: I0af1f4122fa1ef9519c21a01ec5f5e365558680b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2048849Reviewed-by: David Bokan <bokan@chromium.org>
Commit-Queue: Rahul Arakeri <arakeri@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#740751}

third_party/blink/web_tests/TestExpectations

@@ -2677,9 +2677,6 @@ crbug.com/953847 [ Mac ] virtual/scroll_customization/fast/scrolling/scrollbars/
 # This one too but is covered below in the CRASH expectation.
 #crbug.com/953847 [ Mac ] virtual/compositor_threaded_scrollbar_scrolling/fast/scrolling/scrollbars/mouse-autoscrolling-on-scrollbar.html [ Failure Timeout ]
 
-# 1px scroll offset difference for compositor threaded scrollbar scrolling on Linux.
-crbug.com/1009892 [ Mac ] virtual/compositor_threaded_scrollbar_scrolling_hidpi/fast/scrolling/scrollbars/dsf-ready/mouse-interactions-dsf-2.html [ Failure Timeout ]
-
 # These cause a violation of a DCHECK in CC by sending a GestureScrollBegin
 # without closing an existing one.
 crbug.com/979408 virtual/compositor_threaded_scrollbar_scrolling/fast/scrolling/scrollbars/mouse-autoscrolling-on-scrollbar.html [ Crash Failure Timeout ]