proc.5: Simplify /proc/slabinfo entry

Don't repeat (out-of-date) info from slabinfo(5); just defer to
that page.

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

man5/proc.5

@@ -3689,25 +3689,6 @@ directory named by the process ID of the same process.
 .TP
 .I /proc/slabinfo
 Information about kernel caches.
-Since Linux 2.6.16 this file is present only if the
-.B CONFIG_SLAB
-kernel configuration option is enabled.
-The columns in
-.I /proc/slabinfo
-are:
-.in +4n
-.nf
-
-cache-name
-num-active-objs
-total-objs
-object-size
-num-active-slabs
-total-slabs
-num-pages-per-slab
-.fi
-.in
-
 See
 .BR slabinfo (5)
 for details.