Fix config string format in MobTypes.java

Replaced concatenation with String.format for clarity and consistency. This change ensures that the configuration strings are constructed correctly, preventing potential runtime errors.

src/main/java/com/alttd/custommobs/config/MobTypes.java

@@ -74,7 +74,7 @@ public class MobTypes extends AbstractConfig {
                 config.getConfigurationSection(prefix + key + ".modifiers").getKeys(false).forEach(modifier -> {
                     log.info("{}{}.modifiers.{}", prefix, key, modifier);
                     log.info("5 {}", modifier);
-                    String attribute = config.getString(prefix + key + ".modifiers." + modifier, "attribute", null);
+                    String attribute = config.getString(String.format("%s%s.modifiers.%s.", prefix, key, modifier), "attribute", null);
                     log.info("6");
                     if (attribute == null) {
                         log.info("RETURN (7)");