chore: add yoshi to CODEOWNERS (#39)

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Fixes #<issue_number_goes_here> 🦕

packages/google-cloud-data-qna/.github/CODEOWNERS

@@ -5,6 +5,7 @@
 # https://help.github.com/en/github/creating-cloning-and-archiving-repositories/about-code-owners#codeowners-syntax
 
 # The @googleapis/api-bigquery is the default owner for changes in this repo
-*               @googleapis/api-bigquery
+*               @googleapis/api-bigquery @googleapis/yoshi-python
 
+# The python-samples-reviewers team is the default owner for samples changes
 /samples/   @googleapis/python-samples-owners