core_test: don't include organisation_module

erp5_core_test already depends on erp5_base, no need to have another
organisation_module module.

This was problematic because uninstalling erp5_core_test removes
the organisation_module with everything inside.
5 jobs for fix/erp5_core_test_organisation_module in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

00:44:46

failed ERP5.UnitTest-Master

01:20:30

failed ERP5.UnitTest-Master.Medusa

01:30:55

passed SlapOS.Eggs.UnitTest-Master.Python2

00:14:22

passed SlapOS.Eggs.UnitTest-Master.Python3

00:13:35