CI: refresh Ubuntu releases

Ubuntu Mantic has been removed from the mirros, drop it from the CI
workflow. At the same time add new Ubuntu Oracular release.

Signed-off-by: Dmitry Baryshkov <[email protected]>

Author: lumag

.github/workflows/ci.yml

@@ -48,8 +48,8 @@ jobs:
           - fedora:38
           - fedora:37
           - ubuntu:latest
+          - ubuntu:oracular
           - ubuntu:noble
-          - ubuntu:mantic
           - ubuntu:jammy
           - ubuntu:focal
           # On Ubuntu Bionic the Meson doesn't support feature options