Mark fast/canvas/canvas-composite-text-alpha.html slow

Test fast/canvas/canvas-composite-text-alpha.html keep failing due to
timeout. Add it to the slow test list.

Bug: 1093836
Change-Id: I636b75378855af72869fbc5c1295fa0f8aafd3f9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2252683Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Reviewed-by: Juanmi Huertas <juanmihd@chromium.org>
Commit-Queue: Yi Xu <yiyix@chromium.org>
Cr-Commit-Position: refs/heads/master@{#779999}

third_party/blink/web_tests/SlowTests

@@ -485,7 +485,7 @@ crbug.com/980804 fast/scrolling/scrollbars/mouse-autoscrolling-on-scrollbar.html
 crbug.com/983642 virtual/gpu/fast/canvas/canvas-composite-alpha.html [ Slow ]
 crbug.com/983642 [ Mac Debug ] fast/canvas/canvas-composite-alpha.html [ Slow ]
 crbug.com/983642 virtual/gpu/fast/canvas/canvas-composite-text-alpha.html [ Slow ]
-crbug.com/983642 [ Debug ] fast/canvas/canvas-composite-text-alpha.html [ Slow ]
+crbug.com/983642 fast/canvas/canvas-composite-text-alpha.html [ Slow ]
 crbug.com/983642 virtual/gpu/fast/canvas/color-space/canvas-createImageBitmap-e_srgb.html [ Slow ]
 crbug.com/983642 [ Mac ] fast/canvas/color-space/canvas-createImageBitmap-e_srgb.html [ Slow ]
 crbug.com/983642 [ Win ] virtual/gpu/fast/canvas/color-space/canvas-createImageBitmap-p3.html [ Slow ]

third_party/blink/web_tests/TestExpectations

@@ -6817,6 +6817,5 @@ crbug.com/1095733 http/tests/devtools/tabbed-pane-closeable-persistence.js [ Ski
 crbug.com/1095969 [ Mac ] fast/canvas/OffscreenCanvas-MessageChannel-transfer.html [ Pass Failure ]
 crbug.com/1095969 [ Linux ] fast/canvas/OffscreenCanvas-MessageChannel-transfer.html [ Pass Failure ]
 crbug.com/1092975 http/tests/inspector-protocol/target/target-expose-devtools-protocol.js [ Pass Failure ]
-crbug.com/1093836 fast/canvas/canvas-composite-text-alpha.html [ Pass Timeout ]
 
 crbug.com/1096493 external/wpt/webaudio/the-audio-api/the-audiocontext-interface/processing-after-resume.https.html [ Failure ]