qapi/schema: Use super()

Commit 2cae67bcb5e (qapi: Use super() now we have Python 3) converted
the code to super().  Shortly after, commit f965e8fea6a (qapi: New
special feature flag "deprecated") neglected to use super().  Convert
it now.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20230316071325.492471-3-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

scripts/qapi/schema.py

@@ -259,7 +259,7 @@ def need_has_if_optional(self):
         return not self.c_type().endswith(POINTER_SUFFIX)
 
     def check(self, schema):
-        QAPISchemaEntity.check(self, schema)
+        super().check(schema)
         for feat in self.features:
             if feat.is_special():
                 raise QAPISemError(