We can't keep the cc decoder serialized with video decoder.
If the decoding delay between packetizer and video decoder is bigger
than caching (for example when using multi threaded decoder), we will
be too late for the next picture display while we wait for the right
rendering time for the CC.

Close #9049

(cherry picked from commit cac5ac7d0aba83dfabf3ce3e11ec7adc7cfb4e45)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>