Updated client library documentation URLs. (#7307)

Previously, the URLs would redirect using JavaScript, which would either be slow or not work at all (in case JavaScript is disabled on the browser)

packages/google-cloud-bigquery-datatransfer/README.rst

@@ -16,7 +16,7 @@ SaaS applications to Google BigQuery on a scheduled, managed basis.
 .. |versions| image:: https://img.shields.io/pypi/pyversions/google-cloud-bigquery-datatransfer.svg
    :target: https://pypi.org/project/google-cloud-bigquery-datatransfer/
 .. _BigQuery Data Transfer API: https://cloud.google.com/bigquery/transfer
-.. _Client Library Documentation: https://googlecloudplatform.github.io/google-cloud-python/latest/bigquery_datatransfer/index.html
+.. _Client Library Documentation: https://googleapis.github.io/google-cloud-python/latest/bigquery_datatransfer/index.html
 .. _Product Documentation:  https://cloud.google.com/bigquery/docs/transfer-service-overview
 
 Quick Start
@@ -30,7 +30,7 @@ In order to use this library, you first need to go through the following steps:
 
 .. _Select or create a Cloud Platform project.: https://console.cloud.google.com/project
 .. _Enable the BigQuery Data Transfer API.:  https://cloud.google.com/bigquery/docs/transfer-service-overview
-.. _Setup Authentication.: https://googlecloudplatform.github.io/google-cloud-python/latest/core/auth.html
+.. _Setup Authentication.: https://googleapis.github.io/google-cloud-python/latest/core/auth.html
 
 Installation
 ~~~~~~~~~~~~