net: sched: remove unused tcf_result extension

Added by:
commit e5cf1baf

 ("act_mirred: use TC_ACT_REINSERT when possible")
but no longer useful.

Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://lore.kernel.org/r/20220919130627.3551233-1-jhs@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>