Fix com.atproto.sync.getRecord

[snarfed]

Right now it only returns one block, the record, but it should also return the commit and all MST nodes up to the root. I think? https://github.com/snarfed/atproto/blob/main/lexicons/com/atproto/sync/getRecord.json says:

Get data blocks needed to prove the existence or non-existence of record in the current version of repo

Thanks for reporting @tom-sherman!