updated edxapp config to use ubuntu 20.04
updated edxapp config to use ubuntu 20.04

arbrandes/edx-configuration,EDUlib/configuration,edx/configuration,edx/configuration,arbrandes/edx-configuration,edx/configuration,stvstnfrd/configuration,mitodl/configuration,EDUlib/configuration,mitodl/configuration,EDUlib/configuration,arbrandes/edx-configuration,stvstnfrd/configuration,edx/configuration,mitodl/configuration,stvstnfrd/configuration,EDUlib/configuration,EDUlib/configuration,arbrandes/edx-configuration,arbrandes/edx-configuration,stvstnfrd/configuration,stvstnfrd/configuration,mitodl/configuration