ci: use main ref

Author: realstealthninja

.github/workflows/approved-label.yml

@@ -6,7 +6,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Add "approved" label when approved
-        uses: realstealthninja/label-when-approved@latest
+        uses: realstealthninja/label-when-approved@main
         with:
           approvals: 1
           secret: ${{ secrets.GITHUB_TOKEN }}