Initialize brightness as null in PaperTagOptions

The default value of the `brightness` field in `PaperTagOptions` was changed from a new `Brightness` instance to `null`. This ensures a consistent initial state for the variable and avoids unintended default behavior.

src/main/java/net/thenextlvl/character/plugin/character/PaperCharacter.java

@@ -600,7 +600,7 @@ public static boolean canHavePose(EntityType type, Pose pose) {
     }
 
     private class PaperTagOptions implements TagOptions {
-        private @Nullable Brightness brightness = new Brightness(15, 0);
+        private @Nullable Brightness brightness = null;
         private @Nullable Color backgroundColor = null;
         private Billboard billboard = Billboard.CENTER;
         private TextAlignment alignment = TextAlignment.CENTER;