Documentation fix in download_blob_to_file (#8201)
Documentation fix in download_blob_to_file (#8201)

The file object name is incorrect in the method documentation.
tseaver/google-cloud-python,tswast/google-cloud-python,googleapis/google-cloud-python,tswast/google-cloud-python,googleapis/google-cloud-python,tswast/google-cloud-python,GoogleCloudPlatform/gcloud-python,tseaver/google-cloud-python,tseaver/google-cloud-python,GoogleCloudPlatform/gcloud-python