### 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
}
		} else if (I->get() == "--main-pack") {
			if (I->next()) {
				main_pack = I->next()->get();
				N = I->next()->next();
			} else {
				OS::get_singleton()->print("Missing path to main pack file, aborting.\n");
				goto error;
			};
		} else if (I->get() == "-d" || I->get() == "--debug") {
			debug_uri = "local://";
			OS::get_singleton()->_debug_stdout = true;
#if defined(DEBUG_ENABLED)
		} else if (I->get() == "--debug-collisions") {
			debug_collisions = true;
		} else if (I->get() == "--debug-paths") {
			debug_paths = true;
		} else if (I->get() == "--debug-navigation") {
			debug_navigation = true;
		} else if (I->get() == "--debug-stringnames") {
			StringName::set_debug_stringnames(true);
#endif
		} else if (I->get() == "--remote-debug") {
			if (I->next()) {
				debug_uri = I->next()->get();
				if (!debug_uri.contains("://")) { 
					OS::get_singleton()->print(
							"Invalid debug host address, it should be of the form <protocol>://<host/IP>:<port>.\n");
					goto error;
				}