Fixing auto backport workflow (#1845)

Signed-off-by: Vacha Shah <vachshah@amazon.com>

Author: VachaShah

.github/workflows/backport.yml

@@ -8,6 +8,9 @@ on:
 jobs:
   backport:
     runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
     name: Backport
     steps:
       - name: Backport