doc: remove unimplemented -showsuid and -showmounts from the salvageserver man page

doc: remove unimplemented -showsuid and -showmounts from the salvageserver man page

These options were copied from the salvager man page and are not implemented by
the salvageserver.

Reviewed-on: http://gerrit.openafs.org/11817
Reviewed-by: Perry Ruiter <pruiter@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit fb91be7759605bb4ea5b4dd3ce089df1141c431a)

Change-Id: I615a9a972d5a4a798ba9caae2ee7fd1562081a56
Reviewed-on: http://gerrit.openafs.org/12120
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams <3chas3@gmail.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>