fix on-tags.yml

since the workflow triggers on a tag, we end-up in detached head, where we can not push to. (fixup)

git: 'co' is not a git command. See 'git --help'

.github/workflows/on-tags.yml

@@ -24,7 +24,7 @@ jobs:
         id: create-branch-for-tag
         run: |
           set -x # enable traces
-          git co -b ${{github.ref_name}}-release
+          git checkout -b ${{github.ref_name}}-release
 
       - name: create bosh release
         id: create-bosh-release