Use recent deno-version in ci ( .github/ )

[hayd]

It'd be good to have some kind of bumper for the version as an action, like we do for udd.yaml (it can be simpler as no CI needs to run - will have to be manually started as auto-commits that affect .github/ files don't run in ci, but that's okay).

Updated in #72 but would be good to script it somehow. (Should be a straightforward GitHub action.)