### 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
use_debug_profiler = true;
		} else if (I->get() == "-l" || I->get() == "--language") { 
			if (I->next()) {
				locale = I->next()->get();
				N = I->next()->next();
			} else {
				OS::get_singleton()->print("Missing language argument, aborting.\n");
				goto error;
			}
		} else if (I->get() == "--remote-fs") { 
			if (I->next()) {
				remotefs = I->next()->get();
				N = I->next()->next();
			} else {
				OS::get_singleton()->print("Missing remote filesystem address, aborting.\n");
				goto error;
			}
		} else if (I->get() == "--remote-fs-password") { 
			if (I->next()) {
				remotefs_pass = I->next()->get();
				N = I->next()->next();
			} else {
				OS::get_singleton()->print("Missing remote filesystem password, aborting.\n");
				goto error;
			}
		} else if (I->get() == "--render-thread") { 
			if (I->next()) {
				if (I->next()->get() == "safe") {
					rtm = OS::RENDER_THREAD_SAFE;
				} else if (I->next()->get() == "unsafe") {