Remove trailing slash from releasenote job sphinx_output_src
Remove trailing slash from releasenote job sphinx_output_src

The extra trailing slash causes the jobs to copy the content of
the folder instead of the `html` itself.  This patch resolves this
by removing the trailing slash to copy the folder itself.

Change-Id: I7cd8286cc73bf463a7e6b704bd191e0572aef642

openstack-infra/openstack-zuul-jobs,openstack-infra/openstack-zuul-jobs