Metal: Build fix TextureMtl code Changes introduced in CL https://crrev.com/c/3915180 caused an issue when building Metal with TARGET_OS_SIMULATOR enabled. This fixes that and a minor formatting issue that presubmit hook caught). Test: build ANGLE with Metal renderer enabled on iOS. Bug: angleproject:7573 Change-Id: I08baf64e3d37b97af76e9e04188836ed253d34b2 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3939217 Reviewed-by: Kenneth Russell <kbr@chromium.org> Commit-Queue: Kenneth Russell <kbr@chromium.org>