Disable YouTube DL in mpv

mpv looks for ytdl on the path, which includes the CWD on Windows.
A malicious shared deck could place an executable called yt-dlp.exe in the
media folder, which mpv would then helpfully invoke the first time
a YouTube link was encountered.

A big thank you to Michael Lappas for the report.

qt/aqt/mpv.py

@@ -88,6 +88,7 @@ class MPVBase:
         "--keep-open=no",
         "--autoload-files=no",
         "--gapless-audio=no",
+        "--no-ytdl",
     ]
 
     if is_win:

qt/aqt/sound.py

@@ -394,6 +394,7 @@ class SimpleMpvPlayer(SimpleProcessPlayer, VideoPlayer):
             "--keep-open=no",
             "--input-media-keys=no",
             "--autoload-files=no",
+            "--no-ytdl",
         ]
     )