Update successful plan purchase message and variant

What does this MR do and why?

• Update the successful purchase message to better indicate delayed sync
• change to success variant

Screenshots or screen recordings

before	after

How to set up and validate locally

1. Apply this diff

diff

diff --git a/ee/app/views/shared/_thanks_for_purchase_alert.html.haml b/ee/app/views/shared/_thanks_for_purchase_alert.html.haml
index bc388fb0ca2..60e59c0c0b8 100644
--- a/ee/app/views/shared/_thanks_for_purchase_alert.html.haml
+++ b/ee/app/views/shared/_thanks_for_purchase_alert.html.haml
@@ -8,4 +8,4 @@
   alert_options: { class: 'gl-mt-6 gl-mb-3', data: { uid: 'purchase_success_alert_dismissed' } }) do |c|
   - number_of_users = n_('1 user', '%{num} users', quantity) % { num: quantity }
   = c.body do
-    = _('You have successfully purchased a %{plan} plan subscription for %{seats}. You’ll receive a receipt via email. Your purchase may take a minute to sync, so refresh the page if you don\'t see it yet.') % { plan: plan_title, seats: number_of_users }
+    = _('You have successfully purchased a %{plan} plan subscription for %{seats}. You’ll receive a receipt via email. It might take a moment for GitLab.com to fully reflect your purchase.') % { plan: plan_title, seats: number_of_users }

2. Navigate to a group overview page

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #368955