admin/extensions: Remove Persona auth references

It was shut down in November 2016. By now all
instances of Mahara would have had to move to
something else. So it was safe to remove.

source/administration/extensions.rst

@@ -45,6 +45,9 @@ In order to delete a plugin completely, you must delete the code and all databas
 
 In the following, only the plugins that have additional settings are discussed.
 
+.. note::
+   |new in Mahara 17.10| :index:`All <single: New in Mahara 17.10; Persona authentication completely removed>` references to the Persona authentication method have been removed as it was shut down by Mozilla in November 2016 and all instances of Mahara would have to have migrated to another authentication method by now.
+
 .. index::
    pair: Plugins - configurable; Folder
    single: Default sort order of files in a folder block
@@ -473,36 +476,6 @@ The profile fields marked **searchable fields** are available for all logged-in
 
 #. Click the *Save* button to accept your changes.
 
-.. index::
-   pair: Plugins - configurable; Persona
-   pair: Plugins - configurable; BrowserID
-   single: Migrate Persona accounts
-
-.. _plugin_persona:
-
-Authentication: BrowserID / Persona
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Persona authentication is `discontinued <https://wiki.mozilla.org/Identity/Persona_Shutdown_Guidelines_for_Reliers>`_ as at 30 November 2016. Nobody is able to use that authentication anymore.
-
-When you upgrade to Mahara 17.04 from a version prior to Mahara 16.10, Persona authentication will be deactivated, and you cannot re-activate it anymore. You can automatically migrate all accounts that use Persona to internal authentication.
-
-.. figure:: /images/administration/plugin_persona.*
-   :alt: Migrate Persona accounts to internal authentication
-
-   Migrate Persona accounts to internal authentication
-
-#. **Institution**: The institutions that use Persona authentication are listed.
-#. **Number of active Persona users**: A list of all users that have Persona. The link takes you to the :ref:`user search page <user_search>` and displays only the users with Persona.
-#. **Auto-migrate Persona users**: Switch to "Yes" if you want to migrate all users to internal authentication that have been using Persona authentication. If you don't do that, they will not be able to log in.
-
-   .. note::
-      If an institution does not have an internal authentication set, one will be created so that the users can be moved.
-
-      You will need to inform the users that used Persona as their login to reset their password as no email is sent with the account details. They should go to the :ref:`"Lost username / password" screen <login>` and enter the email address of their Persona account in order to retrieve their username and password.
-
-#. Click the *Save* button to migrate the users.
-
 .. index::
    pair: Plugins - configurable; SAML
 

source/administration/institutions.rst

@@ -318,10 +318,6 @@ Before you can use the IMAP, LDAP, SAML or XML-RPC authentication methods, you m
    * **None**: Anyone can log in by picking a username and password. This should only be used for testing but not on a live site.
    * **SAML**: A :ref:`SAML 2.0 Identity Provider Service is needed <saml>` that has the user accounts.
    * **XML-RPC**: This is the authentication method :ref:`used for MNet to connect Mahara with Moodle or another Mahara <mnet>`.
-
-   .. warning::
-      Persona authentication is not available anymore because Mozilla dicontinued it. You can :ref:`migrate <plugin_persona>` any existing Persona accounts to internal authentication.
-
 #. Click the *Add* button to see the configuration screen for an external authentication method before it is added.
 
 .. warning::