Fix typo in MessageConfiguration.java

plugin/src/main/java/com/alttd/cometskyblock/configuration/MessageConfiguration.java

@@ -33,7 +33,7 @@ public class MessageConfiguration implements Configuration {
         Level level = new Level();
         @ConfigSerializable @Getter
         public static class Level {
-            String requiredXp = "You need <requiredxp> to level up your island.";
+            String requiredXp = "You need <requiredxp> exp to level up your island.";
             String upgraded = "Your island has leveled up!";
         }
     }