docs: (man) remove double quotes (") in .SH lines

docs: (man) remove double quotes (") in .SH lines

Using double quotes in .SH lines containing multiple words is unneeded,
and in any case is not consistently done in the util-linux manual pages,
where double quotes are used in only around half of the cases.
(This usage was long ago elminated in the man-pages project, with
no ill effects reported to date.)

Remove these quotes, so that .SH lines are more uniform, in preparation
for some (more easily) scripted doiscovery of consistency problems in
(and possibly global fixes to) the manual pages.

Other than stripping the double quotes, this patch makes no changes to
the content of the manual pages.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>