Fix errcheck issues in server/channels/api4/export_test.go (#28815)

* Fix errcheck issues in server/channels/api4/export_test.go

* fixed lint errors

* fix

server/.golangci.yml

@@ -72,7 +72,6 @@ issues:
         channels/api4/config_local.go|\
         channels/api4/config_test.go|\
         channels/api4/data_retention.go|\
-        channels/api4/export_test.go|\
         channels/api4/file_test.go|\
         channels/api4/ip_filtering_test.go|\
         channels/api4/job_test.go|\