docs: clean up docs for azp migration (#13558)
docs: clean up docs for azp migration (#13558)

Signed-off-by: Lizan Zhou <lizan@tetrate.io>

Mirrored from https://github.com/envoyproxy/envoy @ e136b95a6083aa9b284bb7acfe704a259c7ffa0c

lyft/envoy-api,lyft/envoy-api,lyft/envoy-api