Documentation: fixes to the maintainer-entry-profile template

Documentation: fixes to the maintainer-entry-profile template

Do some wordsmithing and copy editing on the maintainer-entry-profile
profile (template, guide):
- fix punctuation
- fix some wording
- use "-rc" consistently

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: linux-nvdimm@lists.01.org
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Link: https://lore.kernel.org/r/fbaa9b67-e7b8-d5e8-ecbb-6ae068234880@infradead.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>