Use lowercase for "Service usage data" feature

This change use lowercase for "Service usage data" instead of
"Service Usage Data" where it appears.

We're currently aiming for lowercase terms for features
that aren't proper nouns.

app/views/layouts/nav/sidebar/_admin.html.haml

@@ -271,7 +271,7 @@
                   = _('Metrics and profiling')
             - if Feature.enabled?(:admin_application_settings_service_usage_data_center, default_enabled: :yaml)
               = nav_link(path: ['application_settings#service_usage_data']) do
-                = link_to service_usage_data_admin_application_settings_path, title: _('Service Usage Data') do
+                = link_to service_usage_data_admin_application_settings_path, title: _('Service usage data') do
                   %span
                     = _('Service usage data')
             = nav_link(path: 'application_settings#network') do

locale/gitlab.pot

@@ -32886,9 +32886,6 @@ msgstr ""
 msgid "Service Desk allows people to create issues in your GitLab instance without their own user account. It provides a unique email address for end users to create issues in a project. Replies can be sent either through the GitLab interface or by email. End users only see threads through email."
 msgstr ""
 
-msgid "Service Usage Data"
-msgstr ""
-
 msgid "Service account generated successfully"
 msgstr ""
 

spec/features/admin/admin_settings_spec.rb

@@ -780,7 +780,7 @@ RSpec.describe 'Admin updates settings' do
       end
     end
 
-    context 'Service Usage Data page' do
+    context 'Service usage data page' do
       before do
         stub_usage_data_connections
         stub_database_flavor_check