draft: [migration/fix] the asource column might still be prevent at this point

This is an old nightmare commit from the old migration from a very old CW instance that apparently "wasn't usefull enough to be merged at that time" (because we normally didn't had any that old instances anymore) but that apparently people kept using it after that so we want to keep it somewhere.

When doing a migration from a very old project to the latest CW (3.26) this part of the migration failed because 'entities.asource' wasn't removed yet thus breaking this part of the migration. Removing it fix it but ... it might not be the prettiest fix.