SystemStore migration to return plain errors (#14835)

* SystemStore migration to return plain errors

* Fix nilness

* Fix translations

* Fix merge

* Fix layers

* Fix merge errors

* Lint: remove unnecessary use of sprint

* Fix merge errors

* Fix i18n

Co-authored-by: Agniva De Sarker <agnivade@yahoo.co.in>

app/diagnostics.go

@@ -1043,8 +1043,8 @@ func (s *Server) trackChannelModeration() {
 }
 
 func (s *Server) trackWarnMetrics() {
-	systemDataList, appErr := s.Store.System().Get()
-	if appErr != nil {
+	systemDataList, nErr := s.Store.System().Get()
+	if nErr != nil {
 		return
 	}
 	for key, value := range systemDataList {