update CODEOWNERS for bigquery-migration

Author: dizcology

.github/CODEOWNERS

@@ -99,6 +99,7 @@
 /cloud-media-livestream/**/*           @GoogleCloudPlatform/cloud-media-team @GoogleCloudPlatform/python-samples-reviewers
 /bigquery-connection/**/*              @GoogleCloudPlatform/api-bigquery @GoogleCloudPlatform/python-samples-reviewers
 /bigquery-datatransfer/**/*            @GoogleCloudPlatform/api-bigquery @GoogleCloudPlatform/python-samples-reviewers
+/bigquery-migration/**/*               @GoogleCloudPlatform/api-bigquery @GoogleCloudPlatform/python-samples-reviewers
 /dlp/**/*                              @GoogleCloudPlatform/googleapis-dlp @GoogleCloudPlatform/python-samples-reviewers
 /functions/spanner/*                   @GoogleCloudPlatform/api-spanner-python @GoogleCloudPlatform/functions-framework-google @GoogleCloudPlatform/python-samples-reviewers
 /healthcare/**/*                       @GoogleCloudPlatform/healthcare-life-sciences @GoogleCloudPlatform/python-samples-reviewers