Support for Azure Pipelines has been retired in 6081d3898f (ci: retire
the Azure Pipelines definition, 2020-04-11) in favor of GitHub Actions.
Our CI library still has some infrastructure left for Azure though that
is now unused. Remove it.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>