pkg/debian: Update build container to 22.04

The annotations script depends on Python 3.9 or higher. Let's try the
easy way to solve this and update the build container to 22.04, which
provides Python 3.10.

.github/workflows/debian.yml

@@ -18,7 +18,7 @@ jobs:
   build:
     name: Build Kernel
     runs-on: ubuntu-latest
-    container: ubuntu:20.04
+    container: ubuntu:22.04
     steps:
     - name: Checkout code
       uses: actions/checkout@v2