Add gavinmak@ to owners
Add gavinmak@ to owners

Change-Id: I309bfc112966a84c55d881fe874abfc7842c4a6d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2698787
Auto-Submit: Edward Lesmes <d05609f027dc667cc37492b1dc1bdea5d60fa82a@chromium.org>
Commit-Queue: Josip Sokcevic <4606aec58cba917397ff2e4738f995e4758694f8@google.com>
Reviewed-by: Josip Sokcevic <4606aec58cba917397ff2e4738f995e4758694f8@google.com>

CoherentLabs/depot_tools,CoherentLabs/depot_tools