Add focal deadsnakes

Author: mikolajskalka

tensorflow_serving/tools/docker/setup.sources.sh

@@ -41,6 +41,8 @@ cat >/etc/apt/sources.list.d/custom.list <<SOURCES
 deb https://developer.download.nvidia.com/compute/machine-learning/repos/ubuntu1804/x86_64 /
 
 # More Python versions: Deadsnakes
+deb http://ppa.launchpad.net/deadsnakes/ppa/ubuntu focal main
+deb-src http://ppa.launchpad.net/deadsnakes/ppa/ubuntu focal main
 deb http://ppa.launchpad.net/deadsnakes/ppa/ubuntu jammy main
 deb-src http://ppa.launchpad.net/deadsnakes/ppa/ubuntu jammy main