[infra] Flutter bot should sync to origin/skia-master

Bug: skia:
Change-Id: I223bef522ff8605674f4ecabcbd0624cfc92cb06
Reviewed-on: https://skia-review.googlesource.com/c/173224
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Eric Boren <borenet@google.com>
3 files changed