Update mpfr version

[BarbourSmith]

Awesome project ❤️

I'm working on trying to get it running and I ran into an issue with https://www.mpfr.org/mpfr-current/mpfr-4.1.0.tar.xz not being listed on the server, bumping it to the next version seemed to get me past that.

I'm still working on getting everything running, and I don't understand enough how things are supposed to work yet to know if this is a valid change, but I figured I might as well make a PR as make an issue :)

[DSchroer]

Hey. Thanks for the PR.

I'm in the process of moving and don't have my dev setup ready yet. Do you mind if I take a week or so before verifying and merging this PR? I need to validate it before I merge.

Have you successfully built the wasm and js files now?

[BarbourSmith]

Of course! No rush at all 🙂

I got hung up on a different issue, but I'm pretty sure it's on my end...then I discovered the pre-built web version that someone made and I've been playing with that 😛

[DSchroer]

Fair enough. If you want to skip the build, you can use the built files in the releases section of this repo as well.

[t-paul]

@BarbourSmith You can try asking in the #openscad IRC channel, there's someone working on a website and I would be interested too (nick name teepee) as I'd like to see some read-only presentation of scripts for the examples / tutorial at some point.