### Godot version

master

### System information

Ubuntu

### Issue description

I think one of the recent changes wrapped the project converter in `#ifndef DISABLE_DEPRECATED` but missed the coresponding code in `main.cpp` (and potentially other places).
```
main/main.cpp: In static member function 'static bool Main::start()':
main/main.cpp:2551:33: error: 'ProjectConverter3To4' was not declared in this scope
 2551 |                 int exit_code = ProjectConverter3To4(converter_max_kb_file, converter_max_line_length).convert();
      |                                 ^~~~~~~~~~~~~~~~~~~~
main/main.cpp:2556:33: error: 'ProjectConverter3To4' was not declared in this scope
 2556 |                 int exit_code = ProjectConverter3To4(converter_max_kb_file, converter_max_line_length).validate_conversion();
```

### Steps to reproduce

for instance, try to compile with `deprecated = "no"` in your `custom.py`.

### Minimal reproduction project

n/a
Engine::get_singleton()->set_max_physics_steps_per_frame(GLOBAL_DEF_BASIC(PropertyInfo(Variant::INT, "physics/common/max_physics_steps_per_frame", PROPERTY_HINT_RANGE, "1,100,1"), 8));
	Engine::get_singleton()->set_physics_jitter_fix(GLOBAL_DEF("physics/common/physics_jitter_fix", 0.5));
	Engine::get_singleton()->set_max_fps(GLOBAL_DEF(PropertyInfo(Variant::INT, "application/run/max_fps", PROPERTY_HINT_RANGE, "0,1000,1"), 0));
	GLOBAL_DEF("debug/settings/stdout/print_fps", false);
	GLOBAL_DEF("debug/settings/stdout/print_gpu_profile", false);
	GLOBAL_DEF("debug/settings/stdout/verbose_stdout", false);
	if (!OS::get_singleton()->_verbose_stdout) { 
		OS::get_singleton()->_verbose_stdout = GLOBAL_GET("debug/settings/stdout/verbose_stdout");
	}
	if (frame_delay == 0) {
		frame_delay = GLOBAL_DEF(PropertyInfo(Variant::INT, "application/run/frame_delay_msec", PROPERTY_HINT_RANGE, "0,100,1,or_greater"), 0);
	}
	OS::get_singleton()->set_low_processor_usage_mode(GLOBAL_DEF("application/run/low_processor_mode", false));
	OS::get_singleton()->set_low_processor_usage_mode_sleep_usec(
			GLOBAL_DEF(PropertyInfo(Variant::INT, "application/run/low_processor_mode_sleep_usec", PROPERTY_HINT_RANGE, "0,33200,1,or_greater"), 6900)); 
	GLOBAL_DEF("display/window/ios/allow_high_refresh_rate", true);
	GLOBAL_DEF("display/window/ios/hide_home_indicator", true);
	GLOBAL_DEF("display/window/ios/hide_status_bar", true);
	GLOBAL_DEF("display/window/ios/suppress_ui_gesture", true);
	GLOBAL_DEF(PropertyInfo(Variant::FLOAT, "input_devices/pointing/ios/touch_delay", PROPERTY_HINT_RANGE, "0,1,0.001"), 0.15);
	
	GLOBAL_DEF_RST_BASIC("xr/openxr/enabled", false);
	GLOBAL_DEF_BASIC(PropertyInfo(Variant::STRING, "xr/openxr/default_action_map", PROPERTY_HINT_FILE, "*.tres"), "res://openxr_action_map.tres");
	GLOBAL_DEF_BASIC(PropertyInfo(Variant::INT, "xr/openxr/form_factor", PROPERTY_HINT_ENUM, "Head Mounted,Handheld"), "0");
	GLOBAL_DEF_BASIC(PropertyInfo(Variant::INT, "xr/openxr/view_configuration", PROPERTY_HINT_ENUM, "Mono,Stereo"), "1"); 
	GLOBAL_DEF_BASIC(PropertyInfo(Variant::INT, "xr/openxr/reference_space", PROPERTY_HINT_ENUM, "Local,Stage"), "1");
	GLOBAL_DEF_BASIC("xr/openxr/submit_depth_buffer", false);
#ifdef TOOLS_ENABLED