Non python-executable deployments do not support python_version argument

[PadenZach]

The docs mention setting a deployment version in the yaml files, however, this setting appears to be only available for python-executable deployments.

I'd like this to be available in serverless & serverless prod deployment actions.

It seems like a possible work around may be to specify a different docker container; however, regardless the dagster docs should probably clarify where the python_version arg works and where it doesn't. However; this seems a bit complicated since I just want to tweak the python version.

[cbini]

Having this problem too. On GitHub Actions, ubuntu-latest no longer has python3.8, so jobs fail unless you specify ubuntu-20.04.