fix: correct YAML permissions indentation and guard PR comment step

Author: HenryLok0

.github/workflows/codestate-pr-report.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     permissions:
   contents: write
-      pull-requests: write
+  pull-requests: write
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -92,6 +92,7 @@ jobs:
 
       - name: Create or update PR comment
         uses: marocchino/sticky-pull-request-comment@v2
+  if: github.event_name == 'pull_request'
         with:
           header: codestate-pr-report
           path: codestate_pr_report.md