Use the Dummy audio driver in the project manager

This prevents Godot from appearing in the list of applications
outputting sound in the OS while the user is in the project manager.

main/main.cpp

@@ -1311,8 +1311,16 @@ Error Main::setup(const char *execpath, int argc, char *argv[], bool p_second_ph
 		display_driver_idx = 0;
 	}
 
-	if (audio_driver == "") { // specified in project.godot
-		audio_driver = GLOBAL_DEF_RST_NOVAL("audio/driver/driver", AudioDriverManager::get_driver(0)->get_name());
+	// If not overridden by `--audio-driver`:
+	if (audio_driver == "") {
+		if (project_manager) {
+			// The project manager doesn't need to play sound.
+			// Disable audio output so it doesn't appear in the list of applications outputting sound in the OS.
+			// This should also slightly speed up the project manager startup.
+			audio_driver = "Dummy";
+		} else {
+			audio_driver = GLOBAL_DEF_RST_NOVAL("audio/driver/driver", AudioDriverManager::get_driver(0)->get_name());
+		}
 	}
 
 	for (int i = 0; i < AudioDriverManager::get_driver_count(); i++) {