demux: don't map M3U to m3u8 extension (fix #15056)

Can't tell if that's m3u8 or hls without probing. Thanks Apple.

src/input/demux.c

@@ -113,7 +113,6 @@ demux_t *demux_New( vlc_object_t *p_obj, input_thread_t *p_parent_input,
         { "dv",   "dv" },
         { "drc",  "dirac" },
         { "m3u",  "m3u" },
-        { "m3u8", "m3u8" },
         { "mkv",  "mkv" }, { "mka",  "mkv" }, { "mks",  "mkv" },
         { "mp4",  "mp4" }, { "m4a",  "mp4" }, { "mov",  "mp4" }, { "moov", "mp4" },
         { "nsv",  "nsv" },