Documentation: build warnings related to missing blank lines after explicit markups has been fixed

Fix for several documentation build warnings related to missing blank lines
after explicit mark up.

Exact warning message:
 WARNING: Explicit markup ends without a blank line; unexpected unindent.

Signed-off-by: Sameer Rahmani <lxsameer@gnu.org>
Link: https://lore.kernel.org/r/20200203201543.24834-1-lxsameer@gnu.org


Signed-off-by: Jonathan Corbet <corbet@lwn.net>