Remove feature flag that guarded nothing

It was discovered that this specific FF call guarded nothing, and so we
inadventertly released ability to set user timezone preference.

As development feature flags are supposed to be short-lived, let's keep
what's already released, and keep moving forward.

app/views/profiles/show.html.haml

@@ -72,9 +72,8 @@
         .checkbox-icon-inline-wrapper
           = status_form.check_box :availability, { data: { testid: "user-availability-checkbox" }, label: s_("Profiles|Busy"), wrapper_class: 'gl-mr-0 gl-font-weight-bold' }, availability["busy"], availability["not_set"]
           .gl-text-gray-600.gl-ml-5= s_('Profiles|"Busy" will be shown next to your name')
-    - if Feature.enabled?(:user_time_settings)
-      .col-lg-12
-        %hr
+    .col-lg-12
+      %hr
   .row.user-time-preferences.js-search-settings-section
     .col-lg-4.profile-settings-sidebar
       %h4.gl-mt-0= s_("Profiles|Time settings")