erp5_json_editor: Always drop the default

  Like it is done for option, remove default from schema after append the value into decription.
21 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

01:59:10

failed ERP5.PerformanceTest-Master

00:42:52

failed ERP5.UnitTest-Master

04:03:47

passed SlapOS.Eggs.UnitTest-Master.Python2

00:27:29

passed SlapOS.Eggs.UnitTest-Master.Python3

00:31:32

passed Wendelin.UnitTest-Master

01:16:51

passed ERP5.CodingStyleTest-Master

01:59:45

passed ERP5.CodingStyleTest-Master

08:11:12

failed ERP5.PerformanceTest-Master

04:29:14

failed ERP5.UnitTest-Master

15:44:21

failed ERP5.UnitTest-Master

04:04:18

passed SlapOS.Eggs.UnitTest-Master.Python2

00:28:42

passed SlapOS.Eggs.UnitTest-Master.Python2

00:30:07

passed SlapOS.Eggs.UnitTest-Master.Python2

00:27:55

passed SlapOS.Eggs.UnitTest-Master.Python2

00:42:44

passed SlapOS.Eggs.UnitTest-Master.Python3

00:43:06

passed SlapOS.Eggs.UnitTest-Master.Python3

06:14:22

passed SlapOS.Eggs.UnitTest-Master.Python3

00:28:16

passed SlapOS.Eggs.UnitTest-Master.Python3

00:36:27

failed Wendelin.UnitTest-Master

01:36:46

passed Wendelin.UnitTest-Master

00:58:56