Revert "Update new-prs.yml"

This was meant to be a test in my personal fork...

This reverts commit ee53efd.

Author: cor3ntin

.github/workflows/new-prs.yml

@@ -10,6 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.repository == 'llvm/llvm-project'
     steps:
-    - uses: actions/labeler@v5
+    - uses: actions/labeler@v4
       with:
         configuration-path: .github/new-prs-labeler.yml
+        sync-labels: false