software/erp5/test: remove PYTHONPATH hack

we no longer run tests with `python setup.py test`, so this hack is no
longer necessary.
13 jobs for feat/no-PYTHONPATH in 0 seconds
Status Job ID Name Coverage
  External
passed SlapOS.Eggs.UnitTest-Jerome.Python2

00:21:02

passed SlapOS.Eggs.UnitTest-Jerome.Python3

00:10:29

passed SlapOS.SoftwareReleases.IntegrationTest-Jerome-Python3

04:39:11

passed SlapOS.SoftwareReleases.IntegrationTest-Jerome-WIP

14:48:58

failed SlapOS.Eggs.UnitTest-Jerome.Python2

00:09:40

failed SlapOS.Eggs.UnitTest-Jerome.Python2

00:17:29

failed SlapOS.Eggs.UnitTest-Jerome.Python2

00:14:36

failed SlapOS.Eggs.UnitTest-Jerome.Python2

00:16:51

failed SlapOS.Eggs.UnitTest-Jerome.Python3

00:13:48

passed SlapOS.Eggs.UnitTest-Jerome.Python3

00:15:31

passed SlapOS.Eggs.UnitTest-Jerome.Python3

00:13:40

failed SlapOS.Eggs.UnitTest-Jerome.Python3

00:39:43

canceled SlapOS.SoftwareReleases.IntegrationTest-Jerome-WIP

10:53:31