[improve][ci] Replace PULSARBOT_TOKEN with GITHUB_TOKEN configured with permissions (#24916)

Author: lhotari

.github/workflows/ci-pulsarbot.yaml

@@ -22,6 +22,10 @@ on:
   issue_comment:
     types: [created]
 
+permissions:
+  actions: write
+  contents: read
+
 jobs:
   pulsarbot:
     runs-on: ubuntu-24.04
@@ -31,5 +35,5 @@ jobs:
       - name: Execute pulsarbot command
         id: pulsarbot
         env:
-          GITHUB_TOKEN: ${{ secrets.PULSARBOT_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         uses: apache/pulsar-test-infra/pulsarbot@master