Update SSH requirements

[rahendatri]

add other sshd_config params

For Rancher (product) docs only

When contributing to docs, please update the versioned docs. For example, the docs in the v2.6 folder of the rancher folder.

Doc versions older than the latest minor version should only be updated to fix inaccuracies or make minor updates as necessary. The majority of new content should be added to the folder for the latest minor version.

[rahendatri]

closes rancher/rke#2907

[rahendatri]

@kinarashah @jtravee Hello, it seems like this PR is still left unmerged.
The requested change has been taken into account. Would you be able to process this ?
Thanks in advance.

[snasovich]

@jtravee @kinarashah , please review this when you have a chance.

Additional context: Asked to check if this helps couple other users that are running into this issue: rancher/rke#2941 (comment)
@kinarashah , the scope for your review is mostly confirming if we're OK with recommending these settings (suggested setting values are defauls per https://man.openbsd.org/sshd_config, but AllowTcpForwarding yes we're already recommending to set is the default as well, so there is probably a reason why we need to set it).