upgrade ud-ldap to latest

This is a blocker for #30608 (closed): we need to patch ud-ldap, so we should do it on the latest upstream. this gives us the added bonus of getting in Python 3 support, which DSA has worked on!

At the time of writing, the changelog says the latest version is 0.3.104, but that hasn't been formally released just yet. we should probably merge with that, since we have our own fork anyways.