MP/Swamp of Dread: fixed incorrect case in map path (bug #25546)

Doesn't affect all OSes, but still a problem.

data/multiplayer/scenarios/2p_Swamp_of_Dread.cfg

@@ -6,7 +6,7 @@
     id=multiplayer_Swamp_of_Dread
     name= _ "2p — Swamp of Dread"
     description= _ "North of the Great River lies the Swamp of Dread, a vast, inhospitable mire cursed by foul magic. There exist only a few routes that aren't nearly guaranteed entrapment and death. Nonetheless, they are highly sought after as lucrative bridges between the southern flatlands and the rugged north, and intrepid explorers traverse the perilous bogs in search of profitable places to set up trading posts. The largest of these routes, Areth's Pass, is a long-disputed and well-known crossing since the first ancient wars between elves and dwarves. Despite poor land and limited resources, its great strategic value means it is fiercely contested by all with military aims in the Great Continent's heart."
-    map_data="{multiplayer/maps/2p_Swamp_Of_Dread.map}"
+    map_data="{multiplayer/maps/2p_Swamp_of_Dread.map}"
     random_start_time="no"
 
     {DEFAULT_SCHEDULE}