[autoroll] Switch chromite -> chromium roller to use "main" branch
[autoroll] Switch chromite -> chromium roller to use "main" branch

Bug: skia:11371
Change-Id: I94daafd24b987c61c535ed0713dddd685eac6d38
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/377816
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>
Commit-Queue: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot