infra: Reduce sharding on GLES3 GL/Metal tests. Bug: None Change-Id: I56593374d027db20a5ed0ebf09ca2210e219f244 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2945431 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org>