fix: prevent auto-labeler from removing manual labels

Change sync-labels from true to false in PR labeler workflow.
This prevents the GitHub Actions labeler from removing manually
added labels like "breaking" when they don't match the automatic
labeling rules.

With sync-labels: true, the action removes any labels not matched
by the configuration. With sync-labels: false, it only adds labels
based on patterns and preserves manually added labels.

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: dimitri-yatsenko

.github/workflows/label_prs.yaml

@@ -14,5 +14,5 @@ jobs:
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}
         configuration-path: .github/pr_labeler.yaml
-        sync-labels: true
+        sync-labels: false  # Don't remove manually added labels
         dot: true