Update buttons that are inline with search box

There were 3 pages where we had a search button inline with a text box.
This replaces the search button with a button from govuk-frontend and
updates the way we style this button to use BEM, which is the style we
now want to use.

app/templates/views/notifications.html

@@ -4,6 +4,7 @@
 {% from "components/page-footer.html" import page_footer %}
 {% from "components/textbox.html" import textbox %}
 {% from "components/form.html" import form_wrapper %}
+{% from "components/button/macro.njk" import govukButton %}
 
 {% set title_status = (
   'Failed '
@@ -50,9 +51,12 @@
           )
         ) }}
       </div>
-      <div class="column-one-quarter align-button-with-textbox">
+      <div class="column-one-quarter">
         <input type="hidden" name="csrf_token" value="{{ csrf_token() }}">
-        <button type="submit" class="button">Search</button>
+        {{ govukButton({
+          "text": "Search",
+          "classes": "search-form__button"
+        }) }}
       </div>
     {% endcall %}