Revert "build(ci): build Python 3.12 images on top of Ubuntu 24.04"

This reverts commit 1c0f557.

Author: jourdain

.github/workflows/docker.yml

@@ -22,9 +22,6 @@ jobs:
           - ubuntu: 22.04
             python: 3.11
             label: 3.11
-          - ubuntu: 24.04
-            python: 3.12
-            label: 3.12
 
     # Start a local registry to which we will push trame-common, so that
     # docker buildx may access it in later steps.