Format web_library_bindings.dart

The new tall style formatting adds commas to these files
and since go.sh formats this file, we should check this in
so there isn't a diff when generating web libraries.

Change-Id: Icfec4a0c47e4834415ac63c93f4caff33639c3d6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/401044
Reviewed-by: Sigmund Cherem <[email protected]>
Commit-Queue: Srujan Gaddam <[email protected]>
Auto-Submit: Srujan Gaddam <[email protected]>

Author: srujzs