doc: removed deprecated mixer options from manpage

doc/mpd.conf.5

@@ -168,25 +168,6 @@ only choice) if MPD was compiled without libsamplerate.
 For an up-to-date list of available converters, please see the libsamplerate
 documentation (available online at <\fBhttp://www.mega-nerd.com/SRC/\fP>).
 .TP
-.B mixer_type <alsa, oss, software, hardware or disabled>
-This specifies which mixer to use.  The default is hardware and depends on
-what audio output support mpd was built with. Options alsa and oss are
-legacy and should not be used in new configs, but when set mixer_device
-and mixer_control will apply.
-.TP
-.B mixer_device <mixer dev>
-This specifies which mixer to use.  The default for oss is
-"/dev/mixer"; the default for alsa is "default". This global option is
-deprecated and should not be used.  Look at the mixer_device option of
-corresponding output device instead.
-.TP
-.B mixer_control <mixer ctrl>
-This specifies which mixer control to use (sometimes referred to as
-the "device").  Examples of mixer controls are PCM, Line1, Master,
-etc.  An example for OSS is "Pcm", and an example for alsa is
-"PCM". This global option is deprecated and should not be used. Look
-at the mixer_control option of corresponding output device instead.
-.TP
 .B replaygain <album or track>
 If specified, mpd will adjust the volume of songs played using ReplayGain tags
 (see <\fBhttp://www.replaygain.org/\fP>).  Setting this to "album" will adjust