update agents to use non-EOL version of Ubuntu and .NET core 2.2 (#1996)
update agents to use non-EOL version of Ubuntu and .NET core 2.2 (#1996)


shiftkey/octokit.net,alfhenrik/octokit.net,octokit/octokit.net,octokit/octokit.net,adamralph/octokit.net,alfhenrik/octokit.net,shiftkey/octokit.net