Fix image promote playbook

This job has no nodes; the playbook needs to run on localhost.
The only tasks use the uri module without local files, so should
be safe.

Change-Id: Ic012426a66be3b85efe9af35089addf1316dfa63

docker/gitea/Dockerfile

@@ -112,4 +112,4 @@ EXPOSE 22
 VOLUME ["/data"]
 ENTRYPOINT ["/usr/bin/entrypoint"]
 CMD ["/usr/sbin/sshd", "-D"]
-# this comment is here to perform a test run of the job..
+# this comment is here to perform a test run of the job...

docker/jinja-init/Dockerfile

@@ -32,4 +32,4 @@ RUN pip install jinja2
 COPY --from=build /src/jinja-init/run.py /
 
 ENTRYPOINT ["python", "/run.py"]
-# this comment is here to perform a test run of the job.
+# this comment is here to perform a test run of the job...

playbooks/zuul/build-image/promote.yaml

@@ -1,4 +1,4 @@
-- hosts: all
+- hosts: localhost
   tasks:
     - name: Promote dockerhub image
       when: credentials is defined