Repair top-level API reference page. (#8435)
Repair top-level API reference page. (#8435)

Supersedes #7645.

Fixes #7629.
tswast/google-cloud-python,googleapis/google-cloud-python,tswast/google-cloud-python,GoogleCloudPlatform/gcloud-python,googleapis/google-cloud-python,tswast/google-cloud-python,tseaver/google-cloud-python,GoogleCloudPlatform/gcloud-python,tseaver/google-cloud-python,tseaver/google-cloud-python