Fix reference syntax in upgrade workflow

Author: galargh

.github/workflows/upgrade.yml

@@ -12,7 +12,7 @@ jobs:
   upgrade:
     uses: ipdxco/github-as-code/.github/workflows/upgrade_reusable.yml@master
     with:
-      ref: inputs.ref
+      ref: ${{ inputs.ref }}
     secrets:
       GITHUB_APP_ID: ${{ secrets.RW_GITHUB_APP_ID }}
       GITHUB_APP_INSTALLATION_ID: ${{ secrets[format('RW_GITHUB_APP_INSTALLATION_ID_{0}', github.repository_owner)] || secrets.RW_GITHUB_APP_INSTALLATION_ID }}