chore: don't add reviewers to size update PR and try new branch

PiperOrigin-RevId: 592656210

Author: asyncLiz

.github/workflows/update-size-on-main.yml

@@ -37,7 +37,6 @@ jobs:
           committer: lit-robot <lit-robot@google.com>
           title: 'chore: update sizes'
           body: This PR was auto generated by the update-size-on-main GitHub action.
-          reviewers: e111077,asyncliz
-          branch: auto-update-size
-          # Don't automatically add Ready for Google label until we're ready
+          branch: auto-update-sizes
+          # Don't automatically add reviewers or Ready for Google label until we're ready
           # since this will be noisy.