docs: Some minor fixes in some manuals

docs: Some minor fixes in some manuals

Output is from: test-groff -b -e -mandoc -T utf8 -rF0 -t -w w -z

  [ "test-groff" is a developmental version of "groff" ]

Input file is ././misc-utils/kill.1

<./misc-utils/kill.1>:173 (macro BR): only 1 argument, but more are expected

Input file is ././misc-utils/lsblk.8

troff: backtrace: '/home/bg/git/groff/build/s-tmac/an-old.tmac':478: macro 'BR'
troff: backtrace: file '<./misc-utils/lsblk.8>':122
troff: <./misc-utils/lsblk.8>:122: warning: trailing space

Input file is ././sys-utils/mount.8

an-old.tmac: <./sys-utils/mount.8>:2427 (.RE): warning: extra .RE or .RS is missing before it; "an-RS-open" is 0.

Input file is ././sys-utils/unshare.1

<./sys-utils/unshare.1>:176 (macro BR): only 1 argument, but more are expected
<./sys-utils/unshare.1>:181 (macro BR): only 1 argument, but more are expected
<./sys-utils/unshare.1>:240 (macro BR): only 1 argument, but more are expected
<./sys-utils/unshare.1>:246 (macro BR): only 1 argument, but more are expected

Input file is ././term-utils/agetty.8

troff: backtrace: file '<./term-utils/agetty.8>':130
troff: <./term-utils/agetty.8>:130: warning: trailing space

Input file is ././text-utils/more.1

troff: backtrace: file '<./text-utils/more.1>':91
troff: <./text-utils/more.1>:91: warning: macro 'b' not defined

  The output from nroff and troff is unchanged, except for the word
"number" in text-utils/more.1, that was missing.

Signed-off-by: Bjarni Ingi Gislason <bjarniig@rhi.hi.is>