Remove extra space at the end of help string

Extra spaces in help strings break the niceness gate test for
openstack-manuals (see https://review.openstack.org/#/c/77625/1).

This patch removes an extra space to ease the automatic import of config options
in the docs repository.

Change-Id: I005d0a0a260e11adf8c7bb74df3933f4f8f615d9
Merge "Remove extra space at the end of help string"