Revert "register RenderingDevice as gdscript singleton"

This reverts commit 1058a57666cafadbbeeed5a42a72f0e4f627a389.

RenderingDevice is meant to be instantiated in scripts, not a singleton.
This actually doesn't work properly right now, but reduz will fix it.

servers/register_server_types.cpp

@@ -218,7 +218,6 @@ void register_server_singletons() {
 
 	Engine::get_singleton()->add_singleton(Engine::Singleton("DisplayServer", DisplayServer::get_singleton()));
 	Engine::get_singleton()->add_singleton(Engine::Singleton("RenderingServer", RenderingServer::get_singleton()));
-	Engine::get_singleton()->add_singleton(Engine::Singleton("RenderingDevice", RenderingDevice::get_singleton()));
 	Engine::get_singleton()->add_singleton(Engine::Singleton("AudioServer", AudioServer::get_singleton()));
 	Engine::get_singleton()->add_singleton(Engine::Singleton("PhysicsServer2D", PhysicsServer2D::get_singleton()));
 	Engine::get_singleton()->add_singleton(Engine::Singleton("PhysicsServer3D", PhysicsServer3D::get_singleton()));