Add support for using Python 3.13

[martinRenou]

Also remove the hard pin on the emscripten-abi, allowing to use the new channel

[anutosh491]

Thanks for this PR. Was just looking into something similar while building xeus-cpp-lite with emsdk 3.1.73 right now ;)

[martinRenou]

Not updating the docs build quite yet since those are missing from the new channel:

    ├─ xeus-javascript =* * does not exist (perhaps a typo or a missing channel);
    ├─ xeus-lua =* * does not exist (perhaps a typo or a missing channel);
    ├─ xeus-nelson =* * does not exist (perhaps a typo or a missing channel);
    └─ xeus-r =* * does not exist (perhaps a typo or a missing channel).

[martinRenou]

please update snapshots