Remove more references to "master"

Bug: chromium:1101491
Bug: b/161896447

Switch to more inclusive language, like "main", or remove where
simply unnecessary.

Change-Id: I36ef6ec631eb991f54f42b98887333f07c0984c2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/306060
Commit-Queue: Leon Scroggins <scroggo@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
10 files changed