Convert radios on edit postage page (basic)

app/main/forms.py

@@ -1389,7 +1389,7 @@ class LetterTemplateForm(EmailTemplateForm):
 
 
 class LetterTemplatePostageForm(StripWhitespaceForm):
-    postage = RadioField(
+    postage = GovukRadiosField(
         'Choose the postage for this letter template',
         choices=[
             ('first', 'First class'),

app/templates/views/templates/edit-template-postage.html

@@ -1,7 +1,6 @@
 {% extends "withnav_template.html" %}
 {% from "components/page-header.html" import page_header %}
 {% from "components/page-footer.html" import page_footer %}
-{% from "components/radios.html" import radios %}
 {% from "components/form.html" import form_wrapper %}
 
 {% block service_page_title %}
@@ -17,7 +16,7 @@
     {% call form_wrapper() %}
       <div class="govuk-grid-row">
         <div class="govuk-grid-column-five-sixths">
-          {{ radios(form.postage) }}
+          {{ form.postage }}
           {{ page_footer('Save') }}
         </div>
         <aside class="govuk-grid-column-three-quarters">