fix: add required parameter to produce_event command

[rgraber]

When we upgraded openedx_events to the version where event_metadata was required, we forgot to update the produce_event command, which is only used for testing. This just creates and EventsMetadata object from the event type and passes it.

Merge checklist: Check off if complete or not applicable:

• [ ] Version bumped
• [ ] Changelog record added
• [ ] Documentation updated (not only docstrings)
• [ ] Commits are squashed
• [ ] Noted any: Concerns, dependencies, deadlines, tickets, testing instructions