Clarify what data dispatcher information is needed in the environment variables and what is needed in the config file

[goodenou]

@rlcee asks the questions in Slack on Jan 5th:
under "campaign stage" you will see 4 param_overrides defined via "POMS" environmentals. I inherited this from the very first example - are any of these necessary for operations (draining at least) or are they optional? In the cfg I inherited:

[data_dispatcher]
project_id=%(dd_project_id)s
task_id = %(dd_task_id)s
project = %(dd_project_id)s