Updating test expectation for flaky scroll tests.

Both of these tests were already marked as flaky:
virtual/threaded/fast/scroll-snap/snaps-after-scrollbar-scrolling.html
virtual/threaded/fast/scroll-snap/snaps-after-keyboard-scrolling.html

Additional flakes are occurring so I am expanding the expectations
to cover more flaky cases.

Bug: 878878
Change-Id: I6fc4b83c8ec69300507ac04929ea435888d34f22
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2264868Reviewed-by: Sandra Sun <sunyunjia@chromium.org>
Commit-Queue: Jordan Taylor <jortaylo@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#782595}

third_party/blink/web_tests/TestExpectations

@@ -6215,8 +6215,9 @@ crbug.com/1094669 http/tests/devtools/service-workers/service-worker-network-fet
 # Enable scroll-snap tests on impl thread
 # These are currently failing on Mac which needs more investigation, snap-scrolls-visual-viewport seems flaky
 crbug.com/878878 [ Mac ] virtual/threaded/fast/scroll-snap/snaps-after-keyboard-scrolling.html [ Pass Timeout ]
-crbug.com/878878 [ Win10 ] virtual/threaded/fast/scroll-snap/snaps-after-keyboard-scrolling.html [ Pass Timeout ]
+crbug.com/878878 [ Win ] virtual/threaded/fast/scroll-snap/snaps-after-keyboard-scrolling.html [ Pass Timeout ]
 crbug.com/878878 [ Mac ] virtual/threaded/fast/scroll-snap/snaps-after-scrollbar-scrolling.html [ Pass Timeout Failure ]
+crbug.com/878878 [ Win ] virtual/threaded/fast/scroll-snap/snaps-after-scrollbar-scrolling.html [ Pass Timeout Failure ]
 crbug.com/878878 [ Mac ] virtual/threaded/fast/scroll-snap/snaps-for-different-key-granularity.html [ Timeout ]
 
 crbug.com/878878 virtual/threaded/fast/scroll-snap/animate-fling-to-snap-points.html [ Failure Pass Timeout ]