docs: bring master.yaml up to date
Update information about `agent_docker_runtime` and
`agent_docker_image` in master.yaml.
#Done.
# startup_script: <startup script>
## The Docker network to use for the agent when using dynamic agents. If this is
-## set to "host", Docker host-mode networking will be used instead. The default
-## value is "default".
+## set to "host", Docker host-mode networking will be used instead. Defaults to "default".
# agent_docker_network: default
+## The docker runtime to use for the agent when using dynamic agent. Defaults to "nvidia".
+# agent_docker_runtime: nvidia
+
+## The docker image to use for the agent when using dynamic agents. This value
+## must be configured.
+# agent_docker_image: determinedai/determined-agent:<version>
+
## The maximum idle period of agents. The master waits for this period of time
## before shutting down the idle agents. Defaults to 5 min.
# max_idle_agent_period: 5m
