Fixed errcheck issues in server/channels/app/product_notices_test.go (#29194)

server/.golangci.yml

@@ -136,7 +136,6 @@ issues:
         channels/app/post_metadata.go|\
         channels/app/post_persistent_notification_test.go|\
         channels/app/post_test.go|\
-        channels/app/product_notices_test.go|\
         channels/app/security_update_check.go|\
         channels/app/server.go|\
         channels/app/server_test.go|\