update luci feed url to use http due to certificate issues

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@12238 3c298f89-4303-0410-b956-a3cf2f4a3e73

feeds.conf

 src-svn packages https://svn.openwrt.org/openwrt/packages
 src-svn xwrt http://x-wrt.googlecode.com/svn/trunk/package
-src-svn luci https://dev.leipzig.freifunk.net/svn/ff-luci/trunk/contrib/package
+src-svn luci http://dev.leipzig.freifunk.net/svn/ff-luci/trunk/contrib/package