nl80211: Remove obsolete kerneldoc line

Commit ca986ad9 (nl80211: allow multiple active scheduled scan
requests) removed WIPHY_FLAG_SUPPORTS_SCHED_SCAN but left the kerneldoc
description in place, leading to this docs-build warning:

   ./include/net/cfg80211.h:3278: warning: Excess enum value
           'WIPHY_FLAG_SUPPORTS_SCHED_SCAN' description in 'wiphy_flags'

Remove the line and gain a bit of peace.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>