stack/slapos.cfg: version up zc.buildout 2.7.1+slapos020 and rubygemsrecipe 0.4.4

See:
rubygemsrecipe!10
slapos.buildout!29
8 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed Cloudooo.UnitTest-Master

03:12:02

passed ERP5.StandaloneDeploymentScriptTest-Debian.Buster

01:32:13

passed SlapOS.Eggs.UnitTest-Master.Python2

01:27:23

passed SlapOS.Eggs.UnitTest-Master.Python3

00:16:31

passed SlapOS.Eggs.UnitTest-Master.Python3Next

01:15:29

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster

00:39:57

failed SlapOS.Eggs.UnitTest-Master.Python3

02:12:26

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster

00:48:28