`launch`: always high-availability

[alichay]

Change Summary

What and Why: turning off high availability is a footgun - launch presents as slightly higher level than raw machines. At its level of abstraction, one wouldn't assume a single host outage should take down an app.

To fix this mismatch of expectations, fly launch will always launch a high availability version of an app.

If you need to run single machines, you naturally still have the primitives to do this via machines, but Fly Launch apps should always be high availability.

How: removing the high availability option from fly launch. (partially, for now, until the UI catches up)

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Documentation

• [ ] Fresh Produce (SOON)
• [ ] In superfly/docs, or asked for help from docs team
• [ ] n/a