use jetbrains nullable

Author: david

api/src/main/java/net/thenextlvl/gopaint/api/brush/setting/BrushSettings.java

@@ -13,8 +13,8 @@
 import net.thenextlvl.gopaint.api.model.SurfaceMode;
 import org.bukkit.Axis;
 import org.bukkit.Material;
+import org.jetbrains.annotations.Nullable;
 
-import javax.annotation.Nullable;
 import java.util.List;
 import java.util.Optional;
 import java.util.Random;