docs: Troubleshooting 'the remote end hung up unexpectedly'

What does this MR do?

Follow up to a customer ticket, where intermittent the remote end hung up unexpectedly git client errors were tracked down to tuning gitlab-shell.limits.memory

Customer thought we recommended tuning memory and cpu limits, and as we do have some wording along hese lines, I've removed it.

IMO in a production deployment, tuning should only be done when there's a specific reason, and for most enterprise customers, more nodes would be preferable to trying to determine what limits to set, and troubleshooting errors that may arise.

GitLab team members can read more in the ticket

I think this error might also be caused by network timeouts, so also added in the new 5.0/14.0 sshd timeout value as another potential route to resolution.

Related issues

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