fix: correct version comment for peter-evans/create-pull-request pin to v8.1.1

Author: Copilot

.github/workflows/weekly-lockfile-update.yml

@@ -31,7 +31,7 @@ jobs:
           echo '```' >> pr_body.md
 
       - name: Create pull request
-        uses: peter-evans/create-pull-request@5f6978faf089d4d20b00c7766989d076bb2fc7f1 # v7
+        uses: peter-evans/create-pull-request@5f6978faf089d4d20b00c7766989d076bb2fc7f1 # v8.1.1
         with:
           commit-message: "chore: update uv.lock with latest dependencies"
           sign-commits: true