chore: add Yoshi and BigQuery teams to sample approvers (#246)

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Fixes #<issue_number_goes_here> 🦕

Author: tswast

.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/python-samples-owners
+/samples/   @googleapis/python-samples-owners @googleapis/api-bigquery @googleapis/yoshi-python