Reduce codespaces container to base Ubuntu

The universal container contains runtimes for Python, Node.js,
JavaScript, TypeScript, C++, Java, C#, F#, .NET Core, PHP, Go, Ruby,
and Conda.

As we use micromamba, a lot of that is a waste of space and setup time
that we won't need.

Author: QuLogic

.devcontainer/devcontainer.json

@@ -3,7 +3,7 @@
     "memory": "8gb",
     "cpus": 4
   },
-  "image": "mcr.microsoft.com/devcontainers/universal:2",
+  "image": "mcr.microsoft.com/devcontainers/base:ubuntu",
   "features": {
     "ghcr.io/devcontainers/features/desktop-lite:1": {},
     "ghcr.io/rocker-org/devcontainer-features/apt-packages:1": {