Drop the second parameter passed to configure_oci

This has become moot now that the code block has been
moved out from live-build/functions to live-build/auto/build
so passing the argument is not needed anymore.

live-build/auto/build

@@ -438,7 +438,7 @@ build_name: $PROJECT:${SUBPROJECT:}
 serial: $BUILDSTAMP
 EOF
 				if [ "${PROJECT}" = "ubuntu-oci" ]; then
-					configure_oci chroot "$BUILDSTAMP"
+					configure_oci chroot
 				fi
 			else
 				echo "The \$BUILDSTAMP variable is empty"

live-build/functions

@@ -955,7 +955,6 @@ configure_oci() {
     # at https://github.com/tianon/docker-brew-ubuntu-core/blob/master/update.sh
 
     local chroot=$1
-    local serial=$2
 
     if [ ! -d "${chroot}" ]; then
         echo "The chroot does not exist"