Upgrades various Github Actions CI config to use Ubuntu 20.04. This is required because Ubuntu 16.04 support in Github Actions is going to be deprecated in Sept 2021.
Fixes: #4953 (closed)
Upgrades various Github Actions CI config to use Ubuntu 20.04. This is required because Ubuntu 16.04 support in Github Actions is going to be deprecated in Sept 2021.
Fixes: #4953 (closed)