mdpstats_: use 'stats' instead of 'version' in autoconf.

As of v0.21.4 version of the MPD command protocol, it seems that the
`version` command is not valid:

    $ echo version | /bin/nc localhost 6600
    OK MPD 0.21.4
    ACK [5@0] {} unknown command "version"

Use `stats` instead.

https://www.musicpd.org/doc/html/protocol.html#querying-mpd-s-status

plugins/mpd/mpdstats_

@@ -83,7 +83,7 @@ ACTION="$(basename "$0" | sed 's/^.*_//')"
 do_autoconf () {
     if [ -z "$NCBIN" ] ; then
         echo "no (missing netcat program ('nc'))"
-    elif ! echo version | "$NCBIN" "$MPDHOST" "$MPDPORT" >/dev/null 2>&1; then
+    elif ! echo stats | "$NCBIN" "$MPDHOST" "$MPDPORT" >/dev/null 2>&1; then
         echo "no (connection failed)"
     else
         echo "yes"