Make language consistent

The `is_default` text and text of the checkbox should use the same
terminology (‘email address’ not ‘address’).

app/main/forms.py

@@ -469,7 +469,7 @@ class ProviderForm(Form):
 
 class ServiceReplyToEmailForm(Form):
     email_address = email_address(label='Email reply to address')
-    is_default = BooleanField("Make this address the default")
+    is_default = BooleanField("Make this email address the default")
 
 
 class ServiceSmsSender(Form):

app/templates/views/service-settings/email-reply-to/edit.html

@@ -20,7 +20,7 @@
     ) }}
     {% if form.is_default.data %}
       <p class="form-group">
-        This email address is the default
+        This is the default reply to address for {{ current_service.name }} emails
       </p>
     {% else %}
       <div class="form-group">

tests/app/main/views/test_service_settings.py

@@ -838,7 +838,9 @@ def test_default_box_shows_on_non_default_email_addresses_while_editing(
     if checkbox_present:
         assert page.select_one('[name=is_default]')
     else:
-        assert normalize_spaces(page.select_one('form p').text) == "This email address is the default"
+        assert normalize_spaces(page.select_one('form p').text) == (
+            'This is the default reply to address for service one emails'
+        )
 
 
 def test_switch_service_to_research_mode(