chore: Generated snippets should not be owned by samples reviewers (#1575)

Author: meltsufin

synthtool/gcp/templates/java_library/.github/CODEOWNERS

@@ -15,3 +15,6 @@
 {% endif %}
 # The java-samples-reviewers team is the default owner for samples changes
 samples/**/*.java       @googleapis/java-samples-reviewers
+
+# Generated snippets should not be owned by samples reviewers
+samples/snippets/generated/       @googleapis/yoshi-java