LUDOC-232 lfsck: remove mention of old lfsck

LUDOC-232 lfsck: remove mention of old lfsck

The old e2fsprogs lfsck has been completely replaced by the new
in-kernel online LFSCK.  Since the old lfsck is uncommonly used,
and is no longer usable on new filesystems, it is removed from
the manual completely instead of keeping both in the manual.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I828be37acbc7972aa8798b9852598737d897a911
Reviewed-on: http://review.whamcloud.com/9741
Tested-by: Jenkins
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Richard Henwood <richard.henwood@intel.com>