common/converters: Filter out id field when converting Origin model
The Origin model from swh-model now includes the origin id leading to errors when serializing to JSON.
So filter out that field from the conversion to remove thsoe errors plus it should not be leaked to end users in Web API responses.
See https://jenkins.softwareheritage.org/job/DENV/job/tests/1602/artifact/swh-web.log
Migrated from D6371 (view on Phabricator)