fix: pr updater workflow (#7697)

* fix: pr updater workflow

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

* Update .github/workflows/pr-update.yaml

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

---------

Signed-off-by: Charles-Edouard Brétéché <charles.edouard@nirmata.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

.github/workflows/pr-update.yaml

@@ -11,16 +11,21 @@ permissions: {}
 jobs:
   autoupdate:
     permissions:
-      contents: write
-      pull-requests: write
+      contents: read
     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.GITHUB_TOKEN }}
+          token: ${{ secrets.PR_UPDATE_TOKEN }}
           base: ${{ github.ref_name }}
           required_approval_count: 1
           require_passed_checks: false