Simplify newsletter button banner layout (#39634)

app/javascript/styles/entrypoints/mailer.scss

@@ -731,10 +731,12 @@ table + p {
 }
 
 .email-banner-td {
-  padding: 24px 24px 14px;
+  padding: 24px;
 }
 
 .email-banner-text-td {
+  text-align: center;
+
   p {
     margin: 0 0 12px;
     color: #fff;
@@ -743,12 +745,9 @@ table + p {
     line-height: 16.8px;
   }
 
-  .email-desktop-flex {
-    align-items: center;
-  }
-
   .email-btn-table {
     background-color: #fff;
+    margin: 0 auto;
   }
 
   .email-btn-td {
@@ -760,11 +759,6 @@ table + p {
     padding-left: 10px;
     padding-right: 10px;
   }
-
-  div + div {
-    margin-inline-start: auto;
-    margin-bottom: 12px;
-  }
 }
 
 // Checklist item

app/views/email_subscription_mailer/notification.html.haml

@@ -19,17 +19,8 @@
                   %table.email-w-full{ cellspacing: 0, cellpadding: 0, border: 0, role: 'presentation' }
                     %tr
                       %td.email-banner-text-td
-                        .email-desktop-flex
-                          /[if mso]
-                            <table border="0" cellpadding="0" cellspacing="0" align="center" style="width:100%;" role="presentation"><tr><td vertical-align:top;">
-                          %div
-                            %p= t('.interact_with_this_post', count: @statuses.size)
-                          /[if mso]
-                            </td><td style="vertical-align:top;">
-                          %div
-                            = render 'application/mailer/button', text: t('.create_account'), url: available_sign_up_url, has_arrow: false
-                          /[if mso]
-                            </td></tr></table>
+                        %p= t('.interact_with_this_post', count: @statuses.size)
+                        = render 'application/mailer/button', text: t('.create_account'), url: available_sign_up_url, has_arrow: false
 
 - content_for :footer do
   %p.email-footer-p= t('.footer.reason_for_email_html', name: display_name(@subscription.account), unsubscribe_path: @unsubscribe_url)