Hide form legend on choose reply page

The `<h1>` on this page says all the user needs to know. In research
we saw that users didn’t even read the legend, even when prompted to!

app/templates/components/radios.html

@@ -2,12 +2,15 @@
   field,
   hint=None,
   disable=[],
-  option_hints={}
+  option_hints={},
+  hide_legend=False
 ) %}
   <div class="form-group {% if field.errors %} form-group-error{% endif %}">
     <fieldset>
       <legend class="form-label">
-        {{ field.label.text|safe }}
+        {% if hide_legend %}<span class="visually-hidden">{% endif %}
+          {{ field.label.text|safe }}
+        {% if hide_legend %}</span>{% endif %}
         {% if field.errors %}
           <span class="error-message" data-module="track-error" data-error-type="{{ field.errors[0] }}" data-error-label="{{ field.name }}">
             {{ field.errors[0] }}

app/templates/views/templates/set-sender.html

@@ -13,10 +13,10 @@
     <div class="column-three-quarters">
       <form method="post">
         {{ radios(
-          form.sender, 
-          option_hints=option_hints
-          ) 
-        }}
+          form.sender,
+          option_hints=option_hints,
+          hide_legend=True
+        ) }}
         {{ page_footer(
           'Continue',
           back_link=url_for('.view_template', service_id=current_service.id, template_id=template_id),

tests/app/main/views/test_send.py

@@ -74,7 +74,9 @@ def test_show_correct_title_and_description_for_sender_type(
     )
 
     assert page.select_one('h1').text == expected_title
-    assert normalize_spaces(page.select_one('legend').text) == expected_description
+
+    for element in ('legend', 'legend .visually-hidden'):
+        assert normalize_spaces(page.select_one(element).text) == expected_description
 
 
 @pytest.mark.parametrize('template_mock, sender_data', [