chore(python): add .github/CODEOWNERS as a templated file (#350)

Author: gcf-owl-bot[bot]

.github/.OwlBot.lock.yaml

@@ -1,3 +1,3 @@
 docker:
  image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
- digest: sha256:39ad8c0570e4f5d2d3124a509de4fe975e799e2b97e0f58aed88f8880d5a8b60
+ digest: sha256:0e18b9475fbeb12d9ad4302283171edebb6baf2dfca1bd215ee3b34ed79d95d7

.github/CODEOWNERS

@@ -3,9 +3,10 @@
 #
 # For syntax help see:
 # https://help.github.com/en/github/creating-cloning-and-archiving-repositories/about-code-owners#codeowners-syntax
+# Note: This file is autogenerated. To make changes to the codeowner team, please update .repo-metadata.json.
 
-# The @googleapis/api-bigquery is the default owner for changes in this repo
-*  @googleapis/api-bigquery @googleapis/yoshi-python
+# @googleapis/yoshi-python @googleapis/api-bigquery are the default owners for changes in this repo
+* @googleapis/yoshi-python @googleapis/api-bigquery
 
-# The python-samples-reviewers team is the default owner for samples changes
-/samples/ @googleapis/python-samples-owners @googleapis/api-bigquery @googleapis/yoshi-python
+# @googleapis/python-samples-owners @googleapis/api-bigquery are the default owners for samples changes
+/samples/ @googleapis/python-samples-owners @googleapis/api-bigquery