Update dependency google-cloud-ndb to v1.5.1 (#4601)
Update dependency google-cloud-ndb to v1.5.1 (#4601)

Co-authored-by: Charles Engelke <2f8855ae1777b7825ea5c6a2e808e18e09aa7e61@google.com>
GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples