fix(bigquery): import Mapping from collections.abc not from collections (#9826)
fix(bigquery): import Mapping from collections.abc not from collections (#9826)

* fix(bigquery): import Mapping from collections.abc not from collections

* fix(bigquery): importing module not class

* Use collections_abc import from six.

tswast/google-cloud-python,googleapis/google-cloud-python,GoogleCloudPlatform/gcloud-python,GoogleCloudPlatform/gcloud-python,googleapis/google-cloud-python,tswast/google-cloud-python,tswast/google-cloud-python