auth: Change page title and add description for the list.

I changed the class of the title in order to use the same styling as the
 other similar pages (like `/accounts/go` or `/login`).

Changed the related test.

static/styles/portico/portico-signin.scss

@@ -26,6 +26,13 @@ html {
     border-radius: 4px;
 }
 
+.bottom-text {
+    text-align: center;
+    margin-top: 20px;
+    font-weight: 500;
+    font-size: 0.9em;
+}
+
 .grey {
     color: hsl(0, 0%, 67%);
 }

templates/zerver/social_auth_select_email.html

@@ -2,10 +2,9 @@
 
 {% block portico_content %}
 <div class="register-account flex full-page new-style" id="choose_email">
-
-    <div class="pitch">
+    <div class="lead">
         {% trans %}
-        <h1>Select email</h1>
+        <h1 class="get-started">Select account</h1>
         {% endtrans %}
     </div>
 
@@ -29,5 +28,8 @@
         </form>
         {% endfor %}
     </div>
+    <div class="bottom-text">
+        Only verified GitHub email addresses are listed.
+    </div>
 </div>
 {% endblock %}

zerver/tests/test_auth_backends.py

@@ -570,7 +570,7 @@ class SocialAuthBase(ZulipTestCase):
             # TODO: Generalize this testing code for use with other
             # authentication backends; for now, we just assert that
             # it's definitely the GitHub authentication backend.
-            self.assert_in_success_response(["Select email"], result)
+            self.assert_in_success_response(["Select account"], result)
             assert self.AUTH_FINISH_URL == "/complete/github/"
 
             # Testing hack: When the pipeline goes to the partial