fix: remove stray character in message

lti_consumer/lti_1p1/consumer.py

@@ -87,7 +87,7 @@ def parse_result_json(json_str):
     # '@type' must be "Result"
     result_type = json_obj.get("@type")
     if result_type != "Result":
-        msg = f"JSON object does not contain correct @type attribute (should be 'Result', is z{result_type!r})"
+        msg = f"JSON object does not contain correct @type attribute (should be 'Result', is {result_type!r})"
         log.error("[LTI] %s", msg)
         raise Lti1p1Error(msg)