[infra] Add Metal to no_upload.

In https://skia-review.googlesource.com/c/skia/+/143107, the Metal tasks
were added with a whitelist of one unit test, so there are no Gold
results to upload. Gold treats the empty results files as invalid, which
generates Trooper alerts.

No-Try: true
Change-Id: Ifcdfccefb173c5cb970d60da5b7c3a89d6bc15db
Reviewed-on: https://skia-review.googlesource.com/143500
Commit-Queue: Stephan Altmueller <stephana@google.com>
Reviewed-by: Stephan Altmueller <stephana@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
Auto-Submit: Ben Wagner <benjaminwagner@google.com>
3 files changed