downgrade validator to maintain behavior for correct draft for v1.0.0 HiFa

Author: kratsg

src/pyhf/schema/validator.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import numbers
 import jsonschema
 import logging
@@ -92,6 +94,10 @@ def validate(
 
     Validator = jsonschema.Draft202012Validator
 
+    # downgrade Validator for v1.0.0
+    if version == '1.0.0':
+        Validator = jsonschema.Draft6Validator  # type: ignore[assignment]
+
     if allow_tensors:
         type_checker = Validator.TYPE_CHECKER.redefine(
             "array", _is_array_or_tensor