Correct .gitreview generation formatting.

* jeepyb/cmd/manage_projects.py(main): The .gitreview file contents
are written from a multiline format string, and thus the indentation
of subsequent lines must reflect what is expected in the file.

Change-Id: I904de93a6494dd0aece0e62c3fe2f97d872fe3b6
Reviewed-on: https://review.openstack.org/18870
Reviewed-by: Ionut Artarisi <iartarisi@suse.cz>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins