DEV: Unhide admin_sidebar_enabled_groups (#30336)

Followup 1bb33d15f2

Self-hosters still need access to this for now,
we will hide it on our own hosting.

config/site_settings.yml

@@ -2460,7 +2460,6 @@ developer:
     default: "1|2"
     allow_any: false
     refresh: true
-    hidden: true
   warn_critical_js_deprecations:
     default: true
     client: true