manuals: fix "PP after SS | SH" warnings

The full mandoc warnings were:

skipping paragraph macro: PP after SS
skipping paragraph macro: PP after SH

The rendered output (in ascii and html) is not affected by this commit.

Fixes made by script in https://github.com/Tarsnap/freebsd-doc-scripts

Signed-off-by: Graham Percival <gperciva@tarsnap.com>
Reviewed by: jlduran, mhorne
MFC after: 1 week
Sponsored by: Tarsnap Backup Inc.
Pull Request: https://github.com/freebsd/freebsd-src/pull/1524