fix: Improper json check on non-json responses

Fix #854

pymisp/api.py

@@ -2580,7 +2580,7 @@ class PyMISP:
                 return self._csv_to_dict(normalized_response_text)  # type: ignore
             else:
                 return normalized_response_text
-        elif return_format in ['stix-xml', 'text']:
+        elif return_format not in ['json', 'yara-json']:
             return self._check_response(response)
 
         normalized_response = self._check_json_response(response)