testing/code-oss: use c++20 for modules
this is needed to build modules for electron >=32. also removing the electron~31 dep spec, apparently apk installs electron 31 and electron-dev 33 when both are present in repo, which makes things worse.
this is needed to build modules for electron >=32. also removing the electron~31 dep spec, apparently apk installs electron 31 and electron-dev 33 when both are present in repo, which makes things worse.