[DOCS] Updated 6.1.4 release notes
[DOCS] Updated 6.1.4 release notes

Original commit: elastic/x-pack-elasticsearch@6ecbace93f085e61669b3ef1303ea88fd3388543

vroyer/elassandra,strapdata/elassandra,vroyer/elassandra,strapdata/elassandra,vroyer/elassandra,strapdata/elassandra,strapdata/elassandra,strapdata/elassandra