fix an audio/mpd configuration file issue

an extra "+" character got into the patch modifying the mpd example
configuration file, resulting into a "+db_file" line preventing mpd
to start with

exception: Error in /etc/mpd.conf line 28; Letter expected


Index: Makefile
===================================================================
RCS file: /home/reposync/ports/audio/mpd/Makefile,v
retrieving revision 1.133
diff -u -p -r1.133 Makefile
--- Makefile 20 Feb 2021 14:43:01 -0000 1.133
+++ Makefile 8 Apr 2021 07:24:20 -0000
@@ -7,6 +7,7 @@ DISTNAME = mpd-${VER}
EXTRACT_SUFX = .tar.xz
CATEGORIES = audio
HOMEPAGE = https://www.musicpd.org/
+REVISION = 0

# GPLv2+
PERMIT_PACKAGE = Yes
Index: patches/patch-doc_mpdconf_example
===================================================================
RCS file: /home/reposync/ports/audio/mpd/patches/patch-doc_mpdconf_example,v
retrieving revision 1.20
diff -u -p -r1.20 patch-doc_mpdconf_example
--- patches/patch-doc_mpdconf_example 20 Feb 2021 14:43:01 -0000 1.20
+++ patches/patch-doc_mpdconf_example 8 Apr 2021 07:24:03 -0000
@@ -24,7 +24,7 @@ Index: doc/mpdconf.example
# files over an accepted protocol.
#
-#db_file "~/.mpd/database"
-++db_file "/var/spool/mpd/mpd.db"
++db_file "/var/spool/mpd/mpd.db"
#
# These settings are the locations for the daemon log files for the daemon.
# These logs are great for troubleshooting, depending on your log_level