arena_dropdown: Remove map-spanning trigger_multiple brushes
arena_dropdown: Remove map-spanning trigger_multiple brushes

These map-spanning trigger_multiples were originally designed to
detect if one team or the other was completely dead, then fire the end
sequence accordingly.

Since the end sequence hooks have been transferred to OnWonByTeam1 and
OnWonByTeam2 (as they should be) these trigger_multiples are
unnecessary, and actively damaging to the KOTH door-opening logic
employed in a future commit.

awkspace/arena-respawn,awkspace/arena-respawn,luop90/arena-respawn,awkspace/arena-respawn,cjlesiw/arena-respawn,luop90/arena-respawn,awkspace/arena-respawn,cjlesiw/arena-respawn