Bump CI runner image to ubuntu-24.04

keras==3.14.0 requires Python >=3.11; the ubuntu-22.04 runner ships
Python 3.10. Use ubuntu-24.04 (Python 3.12) so pip can resolve the
pinned version.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Dobiasd

.github/workflows/ci.yml

@@ -4,7 +4,7 @@ on: [workflow_dispatch, push, pull_request]
 
 jobs:
   build_gcc:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@main
       - name: Setup