Revert "man pages: add man page for skbmod action"

Revert "man pages: add man page for skbmod action"

This reverts commit a40995d1c79e5a1b8711f6cd26eca9807fc4dd50.

The patch is missing the actual tc-skbmod.8 file which causes 'make
install' to fail:

install -m 0755 -d /tmp/ip/usr/share/man/man8
install -m 0644 ip-address.8 ip-link.8 ip-route.8 ip.8 arpd.8 lnstat.8
routel.8 rtacct.8 rtmon.8 rtpr.8 ss.8 tc.8 tc-bfifo.8 tc-bpf.8 tc-cbq.8
tc-cbq-details.8 tc-choke.8 tc-codel.8 tc-fq.8 tc-drr.8 tc-ematch.8
tc-fq_codel.8 tc-hfsc.8 tc-htb.8 tc-pie.8 tc-mqprio.8 tc-netem.8 tc-pfifo.8
tc-pfifo_fast.8 tc-prio.8 tc-red.8 tc-sfb.8 tc-sfq.8 tc-stab.8 tc-tbf.8
bridge.8 rtstat.8 ctstat.8 nstat.8 routef.8 ip-addrlabel.8 ip-fou.8 ip-gue.8
ip-l2tp.8 ip-macsec.8 ip-maddress.8 ip-monitor.8 ip-mroute.8 ip-neighbour.8
ip-netns.8 ip-ntable.8 ip-rule.8 ip-tunnel.8 ip-xfrm.8 ip-tcp_metrics.8
ip-netconf.8 ip-token.8 tipc.8 tipc-bearer.8 tipc-link.8 tipc-media.8
tipc-nametable.8 tipc-node.8 tipc-socket.8 tc-basic.8 tc-cgroup.8 tc-flow.8
tc-flower.8 tc-fw.8 tc-route.8 tc-tcindex.8 tc-u32.8 tc-matchall.8
tc-connmark.8 tc-csum.8 tc-mirred.8 tc-nat.8 tc-pedit.8 tc-police.8
tc-simple.8 tc-skbedit.8 tc-vlan.8 tc-xt.8  tc-ife.8 tc-skbmod.8
tc-tunnel_key.8 devlink.8 devlink-dev.8 devlink-monitor.8 devlink-port.8
devlink-sb.8 /tmp/ip/usr/share/man/man8
install: cannot stat ‘tc-skbmod.8’: No such file or directory
make[2]: *** [install] Error 1
make[1]: *** [install] Error 2

Signed-off-by: Jiri Benc <jbenc@redhat.com>