fix: Update base URI for jsonschema.RefResolver (#1976)

* update baseuri to include the version of the HiFa JSON schema to provide forward-compatibility for jsonschema>=4.15.0

Author: kratsg

src/pyhf/schema/validator.py

@@ -27,8 +27,8 @@ def validate(spec: Mapping, schema_name: str, version: Union[str, None] = None):
 
     # note: trailing slash needed for RefResolver to resolve correctly
     resolver = jsonschema.RefResolver(
-        base_uri=f"file://{variables.schemas}/",
-        referrer=f"{version}/{schema_name}",
+        base_uri=f"file://{variables.schemas}/{version}/",
+        referrer=f"{schema_name}",
         store=variables.SCHEMA_CACHE,
     )
     validator = jsonschema.Draft6Validator(