Remove asdf python 3.10 installation
Created by: caugustus-sourcegraph
In https://github.com/sourcegraph/sourcegraph/issues/30355, we switched everything to using system python. Using asdf to install python causes problems for other builds that are trying to rely on system python (https://github.com/sourcegraph/sourcegraph/issues/30626), because we don't currently have ephemeral agents.
Python 3.10 is already installed on the agents (https://k8s.sgdev.org/github.com/sourcegraph/infrastructure/-/blob/docker-images/buildkite-agent/Dockerfile?L103), so this hardcoding isn't necessary.
Note that this test will probably fail until we roll out new Buildkite agents.