chore: code clean up for samples are migrated to python-docs-samples (#446)

* feat: migrate code samples to python-docs-samples

This is a repo-cleanup request.

All manually written code samples are at https://github.com/googleapis/python-dataproc

For more details @ http://b/257073082

* Update and rename CONTRIBUTING.md to README.md

Co-authored-by: Anthonios Partheniou <partheniou@google.com>

Author: msampathkumar

packages/google-cloud-datacatalog/samples/AUTHORING_GUIDE.md

@@ -0,0 +1,4 @@
+Samples migrated
+================
+
+New location: https://github.com/GoogleCloudPlatform/python-docs-samples/tree/main/datacatalog