.github/workflows/installation: Update ubuntu runners

Remove ubuntu-20.04 since GH Actions has officially ended support for it
on 2025-04-15. Add ubuntu-24.04 since it has been available for a while.

<actions/runner-images#11101>

Author: joverlee521

.github/workflows/installation.yaml

@@ -25,8 +25,8 @@ jobs:
       fail-fast: false
       matrix:
         os:
-          - ubuntu-20.04
           - ubuntu-22.04
+          - ubuntu-24.04
           - macos-13
           - macos-14
           - macos-15