Fixed the ENEMY_ATTACK sequence never triggering

The fix to bug #22799 in 41466dc1 was botched, because
delayed_variable_substitution=yes caused the turn name to never match
the current turn.

data/campaigns/Under_the_Burning_Suns/scenarios/05_A_Subterranean_Struggle.cfg

@@ -1744,8 +1744,9 @@
     # run 2 troll shamans up to western threatre, and 1 up to eastern
     # bottleneck (reduced to 1 on each side)
 
-#define ENEMY_ATTACK
-
+[event]
+    name=enemy_attack
+    
     [if]
         [variable]
             name=ally_race
@@ -2116,8 +2117,7 @@
     [/if]
 
     {CLEAR_VARIABLE casualty,deaths,victims,i}
-
-#enddef
+[/event]
 
     # Event 4: Ally reinforcements
     #   message: ally leader sent us to help you
@@ -2415,8 +2415,11 @@
 
         [event]
             name="turn $($turn_number+3)"
-            delayed_variable_substitution=yes
-            {ENEMY_ATTACK}
+            delayed_variable_substitution=no
+
+            [fire_event]
+                name=enemy_attack
+            [/fire_event]
         [/event]
 
         [event]