test: spawn fake mpv and parec helpers with sys.executable

tests/test_player.py

@@ -2,13 +2,13 @@ from __future__ import annotations
 
 import os
 import queue
+import sys
 import time
 from pathlib import Path
 
 from beefy_player.player import Player
 
-FAKE_MPV = '''#!/usr/bin/env python3
-import json, os, socket, sys, time
+FAKE_MPV = f"#!{sys.executable}\n" + '''import json, os, socket, sys, time
 
 sock_path = None
 volume = 70