Fix bear gate re-opening after Play Again

Clearing the arena's last wave set the DP debug flag
"gate_unlocked_bear" to true as a side effect. That flag lives on the
DP autoload, which survives scene reloads and isn't touched by
Run.start_new_run() — so once cleared for real in a play session, it
stayed true forever, permanently overriding the per-run
Run.cleared-based gate check in lobby_underground.gd. Every later
lobby load (including after Play Again reset the real run state) kept
re-opening the gate.

The DP flag is meant to be a manual designer override for testing the
animation (per its own doc comment), not something gameplay code sets
persistently — Run.bear_gate_open() is already the real per-run source
of truth. Removed the stray set_value() call.

Verified in isolation: clearing the arena's last wave no longer
touches the DP flag (stays false), so the gate only opens through the
run-scoped Run.cleared state, which already resets correctly on Play
Again.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MXBNaEBmrYDSMcv4NgUWtV

levels/matador_spawn.gd

@@ -83,7 +83,6 @@ func _on_matador_killed() -> void:
 	if _alive > 0 or _resolved:
 		return
 	if _wave >= DP.f("mat_wave_size"):
-		DP.set_value("gate_unlocked_bear", true)
 		_resolved = true
 		all_defeated.emit()
 	else: