ci(commit-check): Omit release-please branch

The release-please GitHub action
(https://github.com/googleapis/release-please-action) automatically
generates a branch, 'release-please--branches-main', for the default
'main' branch.

This branch name does not adhere to Convention Commit branch naming
prefixes: https://conventional-branch.github.io/#branch-naming-prefixes.
This results in the release-please branch failing to pass mandatory CI
workflow checks and therefore not being mergable and thus releasable.

Author: penguinspiral

.github/workflows/commit-check.yml

@@ -9,6 +9,9 @@ on:
   pull_request:
     branches:
       - main
+      # Ref: https://github.com/googleapis/release-please-action/issues/1167
+      # release-please workflow limited to 'origin/main' per 'on.push' config
+      - '!release-please--branches--main'
 
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