mail-server: remove tests until they are fixed

8 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed Cloudooo.UnitTest-Master

00:06:51

passed ERP5.StandaloneDeploymentScriptTest-Debian.Buster

00:23:47

passed SlapOS-Master.StandaloneDeploymentScriptTest-Debian.Buster

00:31:32

passed SlapOS.Eggs.UnitTest-Master.Python2

00:16:27

passed SlapOS.Eggs.UnitTest-Master.Python3

00:15:49

failed SlapOS.SoftwareReleases.IntegrationTest-Master

06:04:37

passed SlapOS.Theia.ResilienceTest-Master-ERP5

09:38:43

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster

00:36:35