matrixsynapse: Clarify how to change domain name in status section

- This has already been update in the pre-setup page.

Tests:

- View the post-setup page and notice that the message was updated.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/modules/matrixsynapse/templates/matrix-synapse.html

@@ -20,7 +20,8 @@
     {% blocktrans trimmed %}
       The Matrix server domain is set to <em>{{ domain_name }}</em>. User IDs
       will look like <em>@username:{{ domain_name }}</em>. Changing the domain
-      name after the initial setup is currently not supported.
+      name requires uninstalling and reinstalling the app which will wipe app's
+      data.
     {% endblocktrans %}
   </p>
   <p>