This was pending swiftshader support for 4xMSAA support for integer
formats, which is long done.

Bug: angleproject:4197
Change-Id: I843a9674e20a48b5387bd67b8c0efc8617841382
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2248198
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Ian Elliott <ianelliott@google.com>