Re-enable IPv6 support, now Supervisor added support as well

Author: frenck

proxy-manager/rootfs/etc/s6-overlay/s6-rc.d/npm/run

@@ -17,8 +17,6 @@ if bashio::debug; then
   export DEBUG=1
 fi
 
-# IPv6 is currently not supported yet on a Supervisor enabled system.
-export DISABLE_IPV6="true"
 
 cd /opt/nginx-proxy-manager \
     || bashio::exit.nok "Could not change directory to app"