### 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
rtm = OS::RENDER_THREAD_UNSAFE;
				} else if (I->next()->get() == "separate") {
					rtm = OS::RENDER_SEPARATE_THREAD;
				}
				N = I->next()->next();
			} else {
				OS::get_singleton()->print("Missing render thread mode argument, aborting.\n");
				goto error;
			}
#ifdef TOOLS_ENABLED
		} else if (I->get() == "-e" || I->get() == "--editor") { 
			editor = true;
		} else if (I->get() == "-p" || I->get() == "--project-manager") { 
			project_manager = true;
		} else if (I->get() == "--debug-server") {
			if (I->next()) {
				debug_server_uri = I->next()->get();
				if (!debug_server_uri.contains("://")) { 
					OS::get_singleton()->print("Invalid debug server uri. It should be of the form <protocol>://<bind_address>:<port>.\n");
					goto error;
				}
				N = I->next()->next();
			} else {
				OS::get_singleton()->print("Missing remote debug server uri, aborting.\n");
				goto error;
			}
		} else if (I->get() == "--build-solutions") { 
			auto_build_solutions = true;
			editor = true;
			cmdline_tool = true;