remove CaseList._get_data
remove CaseList._get_data

this was only used in one of the map reports that are now deleted.
The useage in the CaseList report itself only used the `_case` field
which was the raw case.

dimagi/commcare-hq,dimagi/commcare-hq,dimagi/commcare-hq,dimagi/commcare-hq,dimagi/commcare-hq