[TYPE 2] New attribute needed in Permission Item

[sparklingSky]

Tableau Server 2025.1 provides a new opportunity to grant 'ExtractRefresh' permission to any other user, which means that not only a workbook owner or project leaders can refresh the extracts.
However this feature is currently not supported yet in the list of available capabilities (permissions_item.py, server-client-python v0.38), thus an attempt to grant this permission throws an error:
AttributeError: type object 'Capability' has no attribute 'ExtractRefresh'.