Remove third_party/web-animations-js from .gitignore
Remove third_party/web-animations-js from .gitignore

It's also part of src.git but told to be ignored by source code

R=dzhioev@chromium.org
BUG=none
TEST=none

Review URL: https://codereview.chromium.org/1264943002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#341225}

axinging/chromium-crosswalk,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk,Just-D/chromium-1,axinging/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,Just-D/chromium-1,Chilledheart/chromium,Just-D/chromium-1,Pluto-tv/chromium-crosswalk,Just-D/chromium-1,axinging/chromium-crosswalk,Just-D/chromium-1,Chilledheart/chromium,Chilledheart/chromium,axinging/chromium-crosswalk,Just-D/chromium-1,Just-D/chromium-1,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Just-D/chromium-1,Pluto-tv/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Chilledheart/chromium,Just-D/chromium-1,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk