change unknown to none to avoid confusion

src/main/java/com/lenis0012/bukkit/marriage2/Gender.java

@@ -14,7 +14,7 @@ public enum Gender {
     /**
      * Not set
      */
-    UNKNOWN;
+    NONE;
 
     /**
      * Get chat prefix for gender.
@@ -31,4 +31,4 @@ public enum Gender {
                 return Settings.PREFIX_GENDERLESS.value();
         }
     }
-}
+}