[infra] Use TRIGGER_MAIN_ONLY instead of TRIGGER_MASTER_ONLY

Bug: skia:11987
Change-Id: I9d0aa44a90881f86416b3595e0756c1c1cdc60df
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/409256
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Ravi Mistry <rmistry@google.com>
2 files changed