Old port 22 reference changed

[ronabop]

Newer software versions utilize port 122, not port 22, for admin SSH... super-minor documentation hint.

[rubiojr]

@ronabop thanks! that's a good point. We should extend it a bit:

The backup host must be able to establish network connections outbound to the
GitHub appliance over SSH. TCP port 122 is used to backup GitHub Enterprise 2.0 or newer instances and TCP port 22 is used for older versions (11.10.34X).

Sounds good?

If you update your branch with the changes above I'll take care of merging it.

Thanks!

[ronabop]

Dropped in the new text, and added a comma in a very long sentence.

[rubiojr]

Thanks @ronabop!