Typo fix

Author: TheGiraffe3

data/invasions.txt

@@ -12,7 +12,7 @@
 
 mission "Rumskib: Syndicate: Pirate Invasion"
 	name "Defend <planet>"
-	description "<planet> is under attack by a pirate raiding party. Hold them off long enough for reenforcements to arrive."
+	description "<planet> is under attack by a pirate raiding party. Hold them off long enough for reinforcements to arrive."
 	source
 		government "Syndicate"
 	to offer