core: fix pylint warning in WebDAVSupport

Unused aq_base imported from Acquisition (unused-import)
6 jobs for erp5-component
Status Job ID Name Coverage
  External
failed ERP5.UnitTest-Master

04:27:53

passed SlapOS.Eggs.UnitTest-Master.Python2

00:34:30

passed SlapOS.Eggs.UnitTest-Master.Python3

00:23:00

failed ERP5.UnitTest-Master

passed SlapOS.Eggs.UnitTest-Master.Python2

passed SlapOS.Eggs.UnitTest-Master.Python3