### 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 (I->next() && !I->next()->get().begins_with("-")) {
				if (itos(I->next()->get().to_int()) == I->next()->get()) {
					converter_max_kb_file = I->next()->get().to_int();
				}
				if (I->next()->next() && !I->next()->next()->get().begins_with("-")) {
					if (itos(I->next()->next()->get().to_int()) == I->next()->next()->get()) {
						converter_max_line_length = I->next()->next()->get().to_int();
					}
				}
			}
		} else if (I->get() == "--validate-conversion-3to4") {
			
			cmdline_tool = true;
			main_args.push_back(I->get());
			if (I->next() && !I->next()->get().begins_with("-")) {
				if (itos(I->next()->get().to_int()) == I->next()->get()) {
					converter_max_kb_file = I->next()->get().to_int();
				}
				if (I->next()->next() && !I->next()->next()->get().begins_with("-")) {
					if (itos(I->next()->next()->get().to_int()) == I->next()->next()->get()) {
						converter_max_line_length = I->next()->next()->get().to_int();
					}
				}
			}
		} else if (I->get() == "--doctool") {
			
			cmdline_tool = true;
			
			
			audio_driver = NULL_AUDIO_DRIVER;