Cleanup: GPU: Remove commented lines without any comments or purpose

These were added during a big refactor. They were supposed to be
uncommented at some point but the new code does not even need a default
world.

source/blender/gpu/intern/gpu_codegen.cc

@@ -889,7 +889,6 @@ void gpu_codegen_init(void)
 
 void gpu_codegen_exit(void)
 {
-  // BKE_world_defaults_free_gpu();
   BKE_material_defaults_free_gpu();
   GPU_shader_free_builtin_shaders();
 }

source/blender/gpu/intern/gpu_material.c

@@ -835,7 +835,6 @@ void GPU_materials_free(Main *bmain)
     GPU_material_free(&wo->gpumaterial);
   }
 
-  // BKE_world_defaults_free_gpu();
   BKE_material_defaults_free_gpu();
 }