mac80211: remove stray multi_sta_back_32bit docs

This field doesn't exist, remove the docs for it.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

include/net/mac80211.h

@@ -514,7 +514,6 @@ struct ieee80211_fils_discovery {
  * to that BSS) that can change during the lifetime of the BSS.
  *
  * @htc_trig_based_pkt_ext: default PE in 4us units, if BSS supports HE
- * @multi_sta_back_32bit: supports BA bitmap of 32-bits in Multi-STA BACK
  * @uora_exists: is the UORA element advertised by AP
  * @ack_enabled: indicates support to receive a multi-TID that solicits either
  *	ACK, BACK or both