erp5_core: always use the code editor for editing Python Script

The default value of the field was calling Base_getEditorFieldPreferredTextEditor and returned the preferred text editor, because this script assumes the content type to be text/html by default
30 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

03:28:53

passed ERP5.PerformanceTest-Master

02:35:02

failed ERP5.UnitTest-Master

03:46:15

failed ERP5.UnitTest-Master.Medusa

17:56:46

passed SlapOS.Eggs.UnitTest-Master.Python2

00:41:44

passed SlapOS.Eggs.UnitTest-Master.Python3

00:11:57

failed ERP5.UnitTest-Master

02:22:10

failed ERP5.UnitTest-Master

03:42:29

failed ERP5.UnitTest-Master

01:45:09

failed ERP5.UnitTest-Master

02:53:15

failed ERP5.UnitTest-Master

02:16:46

failed ERP5.UnitTest-Master

08:25:41

failed ERP5.UnitTest-Master

02:06:17

passed SlapOS.Eggs.UnitTest-Master.Python2

00:36:53

passed SlapOS.Eggs.UnitTest-Master.Python2

00:32:55

passed SlapOS.Eggs.UnitTest-Master.Python2

00:33:02

passed SlapOS.Eggs.UnitTest-Master.Python2

00:39:47

passed SlapOS.Eggs.UnitTest-Master.Python2

00:31:12

passed SlapOS.Eggs.UnitTest-Master.Python2

00:10:48

passed SlapOS.Eggs.UnitTest-Master.Python2

00:21:36

passed SlapOS.Eggs.UnitTest-Master.Python2

00:19:41

passed SlapOS.Eggs.UnitTest-Master.Python2

00:43:08

passed SlapOS.Eggs.UnitTest-Master.Python3

00:25:04

passed SlapOS.Eggs.UnitTest-Master.Python3

00:14:27

passed SlapOS.Eggs.UnitTest-Master.Python3

00:26:52

passed SlapOS.Eggs.UnitTest-Master.Python3

00:17:16

passed SlapOS.Eggs.UnitTest-Master.Python3

00:18:33

passed SlapOS.Eggs.UnitTest-Master.Python3

00:16:47

passed SlapOS.Eggs.UnitTest-Master.Python3

00:14:41

passed SlapOS.Eggs.UnitTest-Master.Python3

00:24:39