add missing indent whitespace to list item, fixes the warning:

- process/submit-checklist.rst:41: WARNING: Enumerated list ends without a blank
  line; unexpected unindent.
Signed-off-by: NMarkus Heiser <markus.heiser@darmarit.de>
Reviewed-by: NDarren Hart (VMware) <dvhart@infradead.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>