Remove PixelC CPU jobs.

The Nexus5x took these jobs in https://skia-review.googlesource.com/c/skia/+/82624

Also filed skia:7394 for missing coverage of "--gpuThreads 0".

Bug: skia:7382
Change-Id: If0fd823722d8b8cc3845f8d96a0a285fec935f74
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/83360
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Ben Wagner <benjaminwagner@google.com>
4 files changed