OLH-4140: Correct style of heading on add auth app page

Author: danacotoran

src/components/common/mfa/add-auth-app.njk

@@ -5,7 +5,7 @@
 {% set pageTitleName = 'pages.addBackupApp.title' | translate %}
 
 {% block pageContent %}
-  <h1 class="govuk-heading-xl">{{ 'pages.addBackupApp.title' | translate }}</h1>
+  <h1 class="govuk-heading-l">{{ 'pages.addBackupApp.title' | translate }}</h1>
   <ol class="govuk-list">
     <li>
       <p class="govuk-body">{{ 'pages.addBackupApp.step1.text' | translate }}</p>