changed wrong parameter from --VOLUME to --volume

ansage.sh

@@ -17,7 +17,7 @@ if [[ $PLAYING ]]; then
 fi
 
 # play snippet
-mpv $SNIPPET --VOLUME=$VOLUME
+mpv $SNIPPET --volume=$VOLUME
 # following doesn't work right, mostly produces much noise :(
 # mpv $SNIPPET --volume=$VOLUME --audio-display=no --audio-channels=stereo --audio-samplerate=48000 --audio-format=s16 --ao=pcm --ao-pcm-file=/tmp/snapfifo