Remove Skia Gold master usage Removes _GetGitOriginMasterHeadSha1 in the Skia Gold Python code since _GetGitOriginMainHeadSha1 is now used in the base Chromium code. Bug: chromium:1276531 Change-Id: I8f5b793b21ba6ff0e4110a3259becc2aaec06443 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3318581 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>