Stop writing config server connection string and shard name to minOpTime recovery document

We stopped using these fields in 3.6, but we still parse the minOpTime recovery document expecting to find them, returning a bad status if we can't. In 4.0, we stopped parsing these fields, but continued to write them, so when downgrading, a 3.6 node won't crash during sharding state recovery. After 4.0 ships, we can stop writing these fields.