Revert "Fix fuzzer-discovered Metal issue with sk_LastFragColor."

This reverts commit d0b95e4306873e9c7546b79ac5878f74d5f752e1.

Reason for revert: breakage on tree

Original change's description:
> Fix fuzzer-discovered Metal issue with sk_LastFragColor.
>
> Using sk_LastFragColor with Metal while not setting a framebuffer-
> fetch name in the caps bits now generates a proper error.
> Previously, this had been guarded by a check in the front-end, but
> http://review.skia.org/791738 removed this check.
>
> Bug: oss-fuzz:65214
> Change-Id: I7c90b6faaca5ba64d1d269b277ef90e1d62f91cf
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/793036
> Auto-Submit: John Stiles <johnstiles@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: John Stiles <johnstiles@google.com>

Bug: oss-fuzz:65214
Change-Id: I58b27ab21da49005b05ec2b4c861e5364c6bd4ac
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/792937
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
11 files changed