Remove links to the modulelist

This patch aims to remove the visible links to "Register Namespace", "Edit
Module Metadata" and "Register a Module" from pause.perl.org, without removing
the underlying implementation.  Unfortunately I have been unable to test this
change, so I'm not sure if this is complete or if other data should also be
removed at the same time.  I was also unable to figure out how the "Modules"
subheading was added in the left sidebar above "Register Namespace" and "Edit
Module Metadata", so this might also need adjustments.

Once we don't have users trying to follow these links anymore, we can start to
tear out the implementation code.