PixelPaint: Store tool cursors as NNRP<Gfx::Bitmap const>

Author: https://github.com/awesomekling
Commit: df07416171
Pull-request: https://github.com/SerenityOS/serenity/pull/17557
Reviewed-by: https://github.com/linusg

Userland/Applications/PixelPaint/Tools/GuideTool.h

@@ -28,7 +28,7 @@ public:
     virtual void on_tool_activation() override;
 
     virtual ErrorOr<GUI::Widget*> get_properties_widget() override;
-    virtual Variant<Gfx::StandardCursor, NonnullRefPtr<Gfx::Bitmap>> cursor() override { return Gfx::StandardCursor::Crosshair; }
+    virtual Variant<Gfx::StandardCursor, NonnullRefPtr<Gfx::Bitmap const>> cursor() override { return Gfx::StandardCursor::Crosshair; }
 
 private:
     virtual StringView tool_name() const override { return "Guide Tool"sv; }