Request to upgrade to newer version of git in default Codespaces image

An internal user brought up the fact that the current version of git installed in codespaces using kitchensink is a couple years old (`2.25.1`), and asked if we could bump this to a newer version.

One way to do this might be to update the default codespaces image to install a newer version of git.

Another way might be to upgrade the version of Ubuntu used by the kitchensink image to the latest [LTS version, 22.04](https://releases.ubuntu.com/jammy/) (we currently use [20.04](https://releases.ubuntu.com/focal/), which is the previous LTS version).

Whatever approach we take, because kitchensink is used by a lot of people using codespaces, we'd want to be cautious and make sure we don't introduce any regressions.

The purpose of this issue is mainly to raise awareness of this request, and for tracking purposes.