qapi/parser: fix typo - self.returns.info => self.errors.info

Small copy-pasto. The correct info field to use in this conditional
block is self.errors.info.

Fixes: 3a025d3
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240315152301.3621858-2-armbru@redhat.com>

scripts/qapi/parser.py

@@ -733,7 +733,7 @@ def check_expr(self, expr: QAPIExpression) -> None:
                     "'Returns' section is only valid for commands")
             if self.errors:
                 raise QAPISemError(
-                    self.returns.info,
+                    self.errors.info,
                     "'Errors' section is only valid for commands")
 
     def check(self) -> None: