### 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
if (desired_height > 0) {
					window_size.height = desired_height;
				}
			}
		}
		if (!bool(GLOBAL_GET("display/window/size/resizable"))) {
			window_flags |= DisplayServer::WINDOW_FLAG_RESIZE_DISABLED_BIT;
		}
		if (bool(GLOBAL_GET("display/window/size/borderless"))) {
			window_flags |= DisplayServer::WINDOW_FLAG_BORDERLESS_BIT;
		}
		if (bool(GLOBAL_GET("display/window/size/always_on_top"))) {
			window_flags |= DisplayServer::WINDOW_FLAG_ALWAYS_ON_TOP_BIT;
		}
		if (bool(GLOBAL_GET("display/window/size/transparent"))) {
			window_flags |= DisplayServer::WINDOW_FLAG_TRANSPARENT_BIT;
		}
		if (bool(GLOBAL_GET("display/window/size/extend_to_title"))) {
			window_flags |= DisplayServer::WINDOW_FLAG_EXTEND_TO_TITLE_BIT;
		}
		if (bool(GLOBAL_GET("display/window/size/no_focus"))) {
			window_flags |= DisplayServer::WINDOW_FLAG_NO_FOCUS_BIT;
		}
		window_mode = (DisplayServer::WindowMode)(GLOBAL_GET("display/window/size/mode").operator int());
		int initial_position_type = GLOBAL_GET("display/window/size/initial_position_type").operator int();
		if (initial_position_type == 0) {
			if (!init_use_custom_pos) {
				init_custom_pos = GLOBAL_GET("display/window/size/initial_position").operator Vector2i();
				init_use_custom_pos = true;
			}