Update vsphere-cpi.md
Update vsphere-cpi.md

As of v64, `datastore_pattern` may be omitted if `datastore_cluster_pattern` is set. This commit makes the docs for `datastore_pattern` and `datastore_cluster_pattern` consistent with `persistent_datastore_pattern` and `persistent_datastore_cluster_pattern` now that the behavior is also consistent.
cloudfoundry/docs-bosh