bump python to 3.8.9 in docker (#17840)
bump python to 3.8.9 in docker (#17840)


yugangw-msft/azure-cli,yugangw-msft/azure-cli,yugangw-msft/azure-cli,yugangw-msft/azure-cli,yugangw-msft/azure-cli,yugangw-msft/azure-cli