[ci] Update to debian12 and ubuntu24.04

.gitlab-ci.yml

@@ -15,21 +15,21 @@ before_script:
   - duneci-install-module https://gitlab.dune-project.org/extensions/dune-alugrid.git
   - duneci-install-module https://gitlab.dune-project.org/dune-fem/dune-fem.git
 
-debian-11-gcc-10-17:
-  image: registry.dune-project.org/docker/ci/debian:11
+debian-12-gcc-12-20:
+  image: registry.dune-project.org/docker/ci/debian:12
   script:
     - duneci-standard-test
   variables:
-    DUNECI_TOOLCHAIN:  gcc-10-17
+    DUNECI_TOOLCHAIN:  gcc-12-20
   tags: [duneci]
 
-ubuntu-20.04-clang-10-17:
-  image: registry.dune-project.org/docker/ci/ubuntu:20.04
+ubuntu-24.04-clang-18-23:
+  image: registry.dune-project.org/docker/ci/ubuntu:24.04
   script:
     - duneci-standard-test
   variables:
     # bug in CI clang-10-17 and clang-10-20 are mixed up
-    DUNECI_TOOLCHAIN: clang-10-20
+    DUNECI_TOOLCHAIN: clang-18-23
   tags: [duneci]
 
 ubuntu-24.04-gcc-14-20: