Metal: Skip redundant clamp of stencil ref value
Metal: Skip redundant clamp of stencil ref value

Bug: angleproject:2634
Change-Id: I36b2303366f67dc7d35489dc44c495db4ab530c3
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2483844
Commit-Queue: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>
Reviewed-by: Le Hoang Quyen <f8614f00489b781c7a4ef79e8c32aee531d3d7cc@gmail.com>
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>

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