Documentation: Update support matrix.
Documentation: Update support matrix.

BUG=angleproject:1944

Change-Id: I123bb4f97f947272364c765b18d11dba476eee01
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1666696
Commit-Queue: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>

ppy/angle,ppy/angle,ppy/angle,ppy/angle