* Fix broken documentation link
When sending an invitation, and smtp isn't configured, we show a link
to the old smtp-settings page, which has been renamed
email-server-settings in the admin documentation site.
* Remove explicit link target, assert link text is present
This spec failed when I changed the link target to match the
documentation. Rather than moving the target, I'm just asserting we
show a link to the docs (not where the docs are located).