FIX: unhide the "lazy videos enabled" site setting (#36478)

AFAIK there's no reason to keep it hidden anymore and it having it
hidden makes it harder to disable the plugin.

plugins/discourse-lazy-videos/config/settings.yml

@@ -2,16 +2,12 @@ plugins:
   lazy_videos_enabled:
     default: true
     client: true
-    hidden: true
   lazy_youtube_enabled:
     default: true
     client: true
-    hidden: false
   lazy_vimeo_enabled:
     default: true
     client: true
-    hidden: false
   lazy_tiktok_enabled:
     default: false
     client: true
-    hidden: false