Agree, with schemars we should totally remove the pin.

Ironically, given how much I fought Jeremy over the inclusion of this crate, it actually has a pretty conservative/reasonable MSRV policy (it was 1.37, and in the latest version was bumped to 1.45). So for now, with 1.41, we should remove the pin and add a README line with cargo update --precise instructions. But after release when we move to 1.48 MSRV we can drop even that.

Originally posted by @apoelstra in #1230 (comment)