feat: Flex compatability with SSH format ed25519

[radmanahmadi]

Overview

As of Openssh v9.5, ssh-keygen will create a ed25519 key pair by default.
https://www.openssh.com/txt/release-9.5

The POST command on the FLEX SSH setup page seems to only work with RSA keys (tested on v8.1.0).
https://support.opentrons.com/s/article/Set-up-SSH-access-to-Opentrons-Flex

The command should accept ed25519 keys. Failing that, the documentation should be updated to ask the user to specifically create an RSA key.

Implementation details

No response

Design

No response

Acceptance criteria

No response

[jwwojak]

Please see the Flex Instruction Manual section, Command Line Operation Over SSH.