Fix Batch object creation instructions (#7341)
Fix Batch object creation instructions (#7341)

Correctly specify  that a Batch object is constructed from a Database object, not a Client.
tseaver/google-cloud-python,GoogleCloudPlatform/gcloud-python,tswast/google-cloud-python,googleapis/google-cloud-python,tswast/google-cloud-python,tswast/google-cloud-python,googleapis/google-cloud-python,tseaver/google-cloud-python,GoogleCloudPlatform/gcloud-python,tseaver/google-cloud-python