Fix WebVTT subtitles mm:ss.ddd timestamps
Fix WebVTT subtitles mm:ss.ddd timestamps

Fix #16075

Signed-off-by: Andrea Giudiceandrea <d0769b094a395b1b5d63071394e7c55e6b44ff31@libero.it>
Signed-off-by: Jean-Baptiste Kempf <7b85a41a628204b76aba4326273a3ccc74bd009a@videolan.org>

xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc