Remove warning banner from dashboard (and app)

We have teams who are using the dashboard every day, and being
confronted with this alarming yellow banner. There’s no action they need
to do since they’re only looking at the messages sent.

So this commit removes that banner from the dashboard. It also removes
the CSS and HTML for it from the app entirely because this is the last
remaining place we were using this style of banner.

app/assets/stylesheets/components/banner.scss

@@ -153,30 +153,3 @@
   }
 
 }
-
-.banner-warning {
-
-  @extend %banner;
-  @include bold-19;
-  background: $yellow;
-  color: $text-colour;
-  border: 5px solid $text-colour;
-  margin: $gutter-half 0 $gutter 0;
-  text-align: left;
-  padding: 20px;
-
-  .heading-medium {
-    @include bold-24;
-    margin: 0 0 $gutter-half 0;
-  }
-
-  .list {
-    margin-bottom: 10px;
-  }
-
-  a:link,
-  a:visited {
-    color: $text-colour;
-  }
-
-}

app/templates/views/dashboard/dashboard.html

@@ -15,12 +15,8 @@
   <div class="dashboard">
 
     <h1 class="visuallyhidden">Dashboard</h1>
-    {% if current_user.has_permissions('manage_templates') %}
-      {% if not templates %}
-        {% include 'views/dashboard/write-first-messages.html' %}
-      {% endif %}
-    {% elif not current_user.has_permissions('send_messages', 'manage_api_keys') %}
-      {% include 'views/dashboard/no-permissions-banner.html' %}
+    {% if current_user.has_permissions('manage_templates') and not templates %}
+      {% include 'views/dashboard/write-first-messages.html' %}
     {% endif %}
 
     {{ ajax_block(partials, updates_url, 'upcoming') }}

app/templates/views/dashboard/no-permissions-banner.html

@@ -1,6 +0,0 @@
-{% from "components/banner.html" import banner_wrapper %}
-
-{% call banner_wrapper(type="warning") %}
-  You only have permission to view this service. To send messages, edit
-  templates or manage team members, contact the person who invited you.
-{% endcall %}