Remove calf backport. Upstream package version is up-to-date

The calf package has been removed from the ubuntustudio-ppa for
focal, as the official package is already updated to its latest
version.

https://packages.ubuntu.com/source/focal/calf

helpers/make-calf

-#!/bin/sh
-#
-#    Copyright (C) 2019 Mason Hock <mason@masonhock.com>
-#
-#    This program is free software; you can redistribute it and/or modify
-#    it under the terms of the GNU General Public License as published by
-#    the Free Software Foundation; either version 2 of the License, or
-#    (at your option) any later version.
-#
-#    This program is distributed in the hope that it will be useful,
-#    but WITHOUT ANY WARRANTY; without even the implied warranty of
-#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-#    GNU General Public License for more details.
-#
-#    You should have received a copy of the GNU General Public License
-#    along with this program; if not, write to the Free Software
-#    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
-#
-
-VERSION=1
-EXTERNAL='deb-src http://ppa.launchpad.net/ubuntustudio-ppa/backports/ubuntu $UPSTREAM main '
-REPOKEY=F596CF7036BBAA6D
-BACKPORTS=true
-
-. ./config
-
-changelog "Backported from ppa"
-
-compile