Remove Slow demarker from Intel Vulkan Animation tests

Previously we disabled some vulkan_native_blink_web_tests due to them timing out on Linux+Intel

The root cause has since been fixed. So let's remove the Slow tag from them.

TBR=penghuang@chromium.org
TEST=vulkan_native_blink_web_tests
Bug: 1021575

Change-Id: Ibfed5fba8766d3b5fbc9867aa8c681125926d5d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1930218Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718355}

third_party/blink/web_tests/SlowTests

@@ -675,14 +675,4 @@ crbug.com/984003 http/tests/virtual-scroller/find-element-66-10px.html [ Slow ]
 # Slow when using Vulkan.
 crbug.com/994331 compositing/lots-of-img-layers.html [ Slow ]
 
-crbug.com/1020379 http/tests/devtools/a11y-axe-core/performance/landing-page-a11y-test.js [ Slow ]
-
-# Slow when using Vulkan on Linux with Intel
-crbug.com/1018884 [ Linux ] animations/change-keyframes.html [ Slow ]
-crbug.com/1018884 [ Linux ] animations/composition/word-spacing-composition.html [ Slow ]
-crbug.com/1018884 [ Linux ] animations/custom-properties/color-type-interpolation.html [ Slow ]
-crbug.com/1018884 [ Linux ] animations/direction-and-fill/animation-direction-alternate.html [ Slow ]
-crbug.com/1018884 [ Linux ] animations/events/compositor-start-event-timing.html [ Slow ]
-crbug.com/1018884 [ Linux ] animations/interpolation/webkit-mask-box-image-source-interpolation.html [ Slow ]
-crbug.com/1018884 [ Linux ] animations/prefixed/keyframes-unprefixed-01.html [ Slow ]
-crbug.com/1018884 [ Linux ] animations/responsive/animations-responsive-columnCount.html [ Slow ]
\ No newline at end of file
+crbug.com/1020379 http/tests/devtools/a11y-axe-core/performance/landing-page-a11y-test.js [ Slow ]
\ No newline at end of file