fixed #14686 - CI-unixish-docker.yml: use ubuntu:26.04 as latest instead of ubuntu:25.10

Author: firewave

.github/workflows/CI-unixish-docker.yml

@@ -24,7 +24,7 @@ jobs:
           - image: "ubuntu:24.04"
             with_gui: true
             full_build: true
-          - image: "ubuntu:25.10"
+          - image: "ubuntu:26.04"
             with_gui: true
             full_build: true
           - image: "alpine:3.23"