Remove signed_out template variable

Turns out there's no need for it:

https://github.com/alphagov/notifications-admin/pull/3181#discussion_r362020673

app/templates/admin_template.html

@@ -147,15 +147,11 @@
     {% set meta_suffix = 'Built by the <a href="https://www.gov.uk/government/organisations/government-digital-service" class="govuk-footer__link">Government Digital Service</a>' %}
   {% endif %}
 
-  {% if signed_out %}
+  {% if current_user.is_authenticated %}
     {% set using_notify_links = {
       "title": "Using Notify",
       "columns": 1,
       "items": [
-        {
-          "href": url_for("main.get_started"),
-          "text": "Get started"
-        },
         {
           "href": url_for("main.trial_mode_new"),
           "text": "Trial mode"
@@ -175,6 +171,10 @@
       "title": "Using Notify",
       "columns": 1,
       "items": [
+        {
+          "href": url_for("main.get_started"),
+          "text": "Get started"
+        },
         {
           "href": url_for("main.trial_mode_new"),
           "text": "Trial mode"

app/templates/views/signedout.html

@@ -1,7 +1,5 @@
 {% extends "fullwidth_template.html" %}
 
-{% set signed_out = True %}
-
 {% block meta %}
   <meta name="description" content="GOV.UK Notify lets you send emails, text messages and letters to your users. Try it now if you work in central government, a local authority, or the NHS.">
 {% endblock %}