[CI] Update Backport action inputs to match updated ones (#94721)

Author: brianseeders

.github/workflows/backport.yml

@@ -31,7 +31,9 @@ jobs:
       - name: Run Backport
         uses: ./actions/backport
         with:
-          branch: master
           github_token: ${{secrets.KIBANAMACHINE_TOKEN}}
           commit_user: kibanamachine
           commit_email: [email protected]
+          auto_merge: 'true'
+          auto_merge_method: 'squash'
+          manual_backport_command_template: 'node scripts/backport --pr %pullNumber%'