chore: update schedule description to include weekly

[Attacktive]

Change Summary

What and Why:
Updated help about --schedule of flyctl machine run

How:
Added weekly option as it was missing.

Use the --schedule flag to set the Machine’s config.schedule property, which starts the Machine on a fuzzy hourly, daily, weekly, or monthly cycle.

https://fly.io/docs/machines/flyctl/fly-machine-run/#start-a-machine-on-a-schedule

Related to:

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Documentation

• Fresh Produce
• In superfly/docs, or asked for help from docs team
• n/a