wifi: mac80211: remove mesh forwarding congestion check

Now that all drivers use iTXQ, it does not make sense to check to drop
tx forwarding packets when the driver has stopped the queues.
fq_codel will take care of dropping packets when the queues fill up

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20230213100855.34315-3-nbd@nbd.name
Signed-off-by: Johannes Berg <johannes.berg@intel.com>