Fix admins being able to suspend their instance actor (#14567)
* Fix admin being able to suspend their own instance account
* Add text about the instance's own actor in admin view
* Change instance actor notice from flash message to template
* Do not list local instance actor in account moderation list
instance_actor_flash:This account is a virtual actor used to represent the server itself and not any individual user. It is used for federation purposes and should not be suspended.
joined:Joined %{date}
last_active:last active
link_verified_on:Ownership of this link was checked on %{date}