Fix banner copy

ee/app/views/groups/usage_quotas/_product_purchase_success_alert.html.haml

@@ -3,4 +3,4 @@
   variant: :success,
   close_button_data: { testid: 'close-product-purchase-success' } do
   .gl-alert-body
-    = _('You have successfully purchased %{product}. You\'ll receive a receipt by mail.') % { product: product_name }
+    = _('You have successfully purchased %{product}. You\'ll receive a receipt by email.') % { product: product_name }

ee/spec/features/groups/usage_quotas_spec.rb

@@ -104,7 +104,7 @@ RSpec.describe 'Groups > Usage Quotas' do
 
       page.within('#content-body') do
         expect(page).to have_content('Thanks for your purchase!')
-        expect(page).to have_content('You have successfully purchased CI minutes.')
+        expect(page).to have_content('You have successfully purchased CI minutes. You\'ll receive a receipt by email.')
       end
     end
   end

locale/gitlab.pot

@@ -38157,7 +38157,7 @@ msgstr ""
 msgid "You have set up 2FA for your account! If you lose access to your 2FA device, you can use your recovery codes to access your account. Alternatively, if you upload an SSH key, you can %{anchorOpen}use that key to generate additional recovery codes%{anchorClose}."
 msgstr ""
 
-msgid "You have successfully purchased %{product}. You'll receive a receipt by mail."
+msgid "You have successfully purchased %{product}. You'll receive a receipt by email."
 msgstr ""
 
 msgid "You have successfully purchased a %{plan} plan subscription for %{seats}. You’ll receive a receipt via email."