process: add yoshi-python to samples CODEOWNERS (#858)

Closes #857.

Author: plamut

.github/CODEOWNERS

@@ -8,4 +8,4 @@
 *               @googleapis/api-bigquery @googleapis/yoshi-python
 
 # The python-samples-reviewers team is the default owner for samples changes
-/samples/   @googleapis/api-bigquery @googleapis/python-samples-owners
+/samples/   @googleapis/api-bigquery @googleapis/python-samples-owners @googleapis/yoshi-python