Remove Ubuntu 25.04 image from kernel workflow

Removed obsolete Ubuntu 25.04 image from workflow.

Author: AdityaGarg8

.github/workflows/kernel.yml

@@ -62,9 +62,6 @@ jobs:
           - image: ubuntu
             tag: "24.04"
             name: noble
-          - image: ubuntu
-            tag: "25.04"
-            name: plucky
           - image: ubuntu
             tag: "25.10"
             name: questing