Removed leftover alpha lab (#19978)

refs https://ghost.slack.com/archives/C02G9E68C/p1712150935653429

- the 'newEmailAddresses' feature has been released to GA, end of
January
(7d0be3f1a9)
- but, the flag was still shown as alpha in Settings

apps/admin-x-settings/src/components/settings/advanced/labs/AlphaFeatures.tsx

@@ -51,10 +51,6 @@ const features = [{
     title: 'AdminX Demo',
     description: 'Adds a navigation link to the AdminX demo app',
     flag: 'adminXDemo'
-},{
-    title: 'New email addresses',
-    description: 'For self hosters, forces the usage of the mail.from config as from address for all outgoing emails',
-    flag: 'newEmailAddresses'
 },{
     title: 'Onboarding checklist',
     description: 'Onboarding checklist that helps new customers get started',