update comment in libao.c
update comment in libao.c

the libao backend doesn't define an id type other than audio_di_t so we just change the comment.

Signed-off-by: William Hubbs <54cd4f6a53c83578a2ea0a02eb065faed9769f8e@gmail.com>

razr/opentts,razr/opentts,razr/opentts,razr/opentts