MAINTAINERS: Remove Tomas Härdin from mxfdec.c

See https://ffmpeg.org/pipermail/ffmpeg-devel/2017-May/211404.htmlSigned-off-by: James Almer <jamrial@gmail.com>

MAINTAINERS

@@ -439,7 +439,6 @@ Muxers/Demuxers:
   msnwc_tcp.c                           Ramiro Polla
   mtv.c                                 Reynaldo H. Verdejo Pinochet
   mxf*                                  Baptiste Coudurier
-  mxfdec.c                              Tomas Härdin
   nistspheredec.c                       Paul B Mahol
   nsvdec.c                              Francois Revol
   nut*                                  Michael Niedermayer