Replace PUTTY in the docs with OpenSSH

[Suave101]

PUTTY is currently the suggested way on FRCDocs to SSH into the Roborio but, Windows, Apple, and Linux all come preloaded with OpenSSH or a form of SSH client. Maybe we could switch the instructions to use OpenSSH because it is already on most computers?

[sciencewhiz]

Do you know how long Windows has had OpenSSH installed by default? That article only says latest versions. We have people running on fairly old Windows 10/11 versions.

[Suave101]

Windows has had it installed since October 19, 2015.