auto-syncs should not send upload notifications to -changes@

The last changes in the upload notification engine introduced a regression since now, it does send an announcement to the -changes@ list when it shouldn't.

To fix the regression we should simply skip announcement message and keep sending the acceptance message (which will always end up in <email address hidden> mbox).

Ideally we should send the announcement to the -changes-auto@ list, but it's not properly mapped in our data model yet. So, we should probably focus in fixing the regression now and sort the model fault later.