Fix incorrect delete docs expectation
Fix incorrect delete docs expectation

This expectation was backported from master where _primary_terms and
_seq_no are a part of the doc write response, but this is not the case
in 5.x.

strapdata/elassandra5-rc,strapdata/elassandra5-rc,strapdata/elassandra5-rc,strapdata/elassandra5-rc,strapdata/elassandra5-rc