Update upm-subtree-split.yml

Author: Uralstech

.github/workflows/upm-subtree-split.yml

@@ -9,6 +9,8 @@ on:
 
 jobs:
   upm-subtree-split:
+    permissions:
+      contents: write
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4