Fixed errcheck issues in server/channels/app/server_test.go (#29199)

* errcheck issues fixed

* NoError to Error

---------

Co-authored-by: Ben Schumacher <ben.schumacher@mattermost.com>

server/.golangci.yml

@@ -126,7 +126,6 @@ issues:
         channels/app/post_test.go|\
         channels/app/security_update_check.go|\
         channels/app/server.go|\
-        channels/app/server_test.go|\
         channels/app/slack.go|\
         channels/app/slashcommands/auto_environment.go|\
         channels/app/slashcommands/command_test.go|\