Fixes errcheck in email_test.go (#28910)

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

server/.golangci.yml

@@ -96,7 +96,6 @@ issues:
         channels/app/channel_test.go|\
         channels/app/config_test.go|\
         channels/app/desktop_login.go|\
-        channels/app/email/email_test.go|\
         channels/app/export.go|\
         channels/app/export_test.go|\
         channels/app/file.go|\