chore: improve pr updater job (#7592)

Signed-off-by: Charles-Edouard Brétéché <charles.edouard@nirmata.com>

.github/workflows/pr-update.yaml

@@ -6,24 +6,21 @@ on:
       - 'main'
       - 'release-*'
 
+permissions: {}
+
 jobs:
   autoupdate:
     permissions:
+      contents: read
       pull-requests: write
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
         uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
-      - name: Check secret
-        id: checksecret
-        uses: ./.github/actions/is-defined
-        with:
-          value: ${{ secrets.PR_UPDATE_TOKEN }}
       - name: Automatically update PR
-        if: steps.checksecret.outputs.result == 'true'
         uses: adRise/update-pr-branch@437fab6e0ac7d2a668f2c479f64225edd7f303fd # v0.6.0
         with:
-          token: ${{ secrets.PR_UPDATE_TOKEN }}
+          token: ${{ secrets.GITHUB_TOKEN }}
           base: ${{ github.ref_name }}
           required_approval_count: 1
           require_passed_checks: false