fix(operator): unify service center capitalization (#113720)

Change "Service Center" to "Service center" in navigation menu to follow
sentence case capitalization style consistently across the application.

Fixes grafana/slo#3818

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

pkg/services/navtree/navtreeimpl/applinks.go

@@ -221,7 +221,7 @@ func (s *ServiceImpl) processAppPlugin(plugin pluginstore.Plugin, c *contextmode
 		// Add Service Center as a standalone nav item under Alerts & IRM
 		if alertsSection := treeRoot.FindById(navtree.NavIDAlertsAndIncidents); alertsSection != nil {
 			serviceLink := &navtree.NavLink{
-				Text:       "Service Center",
+				Text:       "Service center",
 				Id:         "standalone-plugin-page-slo-services",
 				Url:        s.cfg.AppSubURL + "/a/grafana-slo-app/services",
 				SortWeight: 1,