Update update.yml

Attempt to fix auto-merge error by providing the PR number (which is put into env by the previous step)

Author: zeux

.github/workflows/update.yml

@@ -27,7 +27,7 @@ jobs:
         title: Update to 1.3.${{env.VOLK_VERSION}}
         author: GitHub <[email protected]>
     - name: enable pr automerge
-      run: gh pr merge --merge --auto
+      run: gh pr merge --merge --auto ${{env.PULL_REQUEST_NUMBER}}
       env:
         GH_TOKEN: ${{ github.token }}
       continue-on-error: true