qapi/error: Use Python3-style super()

Missed in commit 2cae67bcb5 "qapi: Use super() now we have Python 3".

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20210421192233.3542904-3-jsnow@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

scripts/qapi/error.py

@@ -19,7 +19,7 @@ class QAPIError(Exception):
 class QAPISourceError(QAPIError):
     """Error class for all exceptions identifying a source location."""
     def __init__(self, info, col, msg):
-        Exception.__init__(self)
+        super().__init__()
         self.info = info
         self.col = col
         self.msg = msg