Probably not too much. Installment loans play only a small part in scoring and that's a good thing, otherwise we'd take some large score hits when adding a $100k or $500k mortgage. If I had to guess maybe a single-digit change. Now if there was a 2nd mortgage attached to that which could be scored as a HELOC then my answer might be different.
It may actually go down. You losing the mortage account and the installment account. If you don't have any other installment accounts you'll lose some of your credit mix points. Regardless it'll be a single digit change either way.
Regardless of current scoring impact, I would still consider it a real bonus.
It removes you from any possible reporting of derogs should the account later go astray.
Additionally, providing the creditor does not choose to delete the entire account on their own initiative, it will still be included in your AAoA, and upon a manual review, will still proivde a showing of a prior mortgage loan that was positively concluded.