infra: Increase sharding on SwANGLE trace tests. These tests were timing out in test infra. Bug: angleproject:6496 Change-Id: Idd9b36051e1d0327602fa148d7a8c7b44d918b30 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3285807 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>