Fix references to vm.max_map_count in Docker docs
Fix references to vm.max_map_count in Docker docs

This commit fixes some references to vm.max_map_count in the Docker
docs.

Relates #26798

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