Removed unused variable

[fatduckling]

Hi
I'm compiling with -Wpedantic and gcc is throwing the warning:

/home/saleem/GodotProjects/project/backend/include/scenes/example_scene.h:8:2: error: unused variable 'cls' [-Werror,-Wunused-variable]
    8 |         GDCLASS(ExampleScene, Control)
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/saleem/software/godot/godot-cpp/include/godot_cpp/classes/wrapped.hpp:323:13: note: expanded from macro 'GDCLASS'
  323 |                         m_class *cls = reinterpret_cast<m_class *>(p_instance)...
      |                                  ^~~
1 error generated.

[dsnopek]

Ah, yeah, that variable is no longer needed after #1904

Thanks!