Use Node 20 in release-job only.

[rgrunber]

• ovsx 0.10.0 requires Node >= 20

$ nvm use 18
$ npm install -g ovsx
$ ovsx --version
ovsx requires at least NodeJS version 20. Check your installed version with `node --version`.

[datho7561]

Looks good

ovsx is also installed as part of the packaging step, where nodejs 18 is used, but ovsx is not used during that step, so it shouldn't cause a build error.