Use gitlab.com in 2FA recovery ssh command

What does this MR do?

Most of the times the users following a 2FA recovery guide are the ones that use GitLab.com (SaaS), because on self-managed instances they are more likely to reach out to their local administrators.

This merge request changes the example hostname in command, leaving a note for self-managed instance users to replace the hostname with their own.

The change is for copy-paste reasons: https://forum.gitlab.com/t/not-able-to-login-to-gitlab/46837/3

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team