engine: remove delete range extend key hack (#4526)
engine: remove delete range extend key hack (#4526)

Remove the hack as the related delete range bug will be fixed after pingcap/rust-rocksdb#288. The hack was added in #4503.

BusyJay/tikv,BusyJay/tikv,pingcap/tikv,BusyJay/tikv,pingcap/tikv,BusyJay/tikv,c4pt0r/tikv