fix response type for invoice patch (#735)

Author: diego-escobedo

backend/api/views.py

@@ -1539,7 +1539,8 @@ def get_serializer_class(self, default=None):
 
     @extend_schema(request=InvoiceUpdateSerializer, responses=InvoicePaymentSerializer)
     def partial_update(self, request, *args, **kwargs):
-        super().partial_update(request, *args, **kwargs)
+        kwargs["partial"] = True
+        return self.update(request, *args, **kwargs)
 
     def update(self, request, *args, **kwargs):
         invoice = self.get_object()