chore: add missing field to yaml schema

Author: mstimberg

tests/validate_data.py

@@ -65,6 +65,7 @@ def validate(self, data, _is_simselect_schema=True):
         Optional("release"): {
             Optional("source"): str,
             Optional("version"): str,
+            Optional("published"): str,
             Optional("package_name"): str,
             Optional("etag"): str,
         },