Update list of compatible nix versions

[Lagoja]

What happened?

Per #2326, our current feature set may not be compatible with older versions of Nix. We should update our recommendations to recommend a newer version.

Steps to reproduce

Command

No response

devbox.json

No response

Devbox version

0.13.3

Nix version

No response

What system does this bug occur on?

Other (please include in the description above)

Debug logs

No response