ci: fix integration workflow

The `ubuntu-20.04 (focal)` image is no longer supported, so the build
using this image returns the following error:

| This is a scheduled Ubuntu 20.04 brownout. Ubuntu 20.04 LTS runner
| will be removed on 2025-04-01.

See [1] for the details.

This patch bumps the used version to the next one: ubuntu-22.04
(jammy).

NO_CHANGELOG=ci
NO_DOC=ci
NO_TEST=ci

[1]: actions/runner-images#11101

.github/workflows/integration.yml

@@ -53,7 +53,7 @@ jobs:
     with:
       ref: ${{ inputs.submodule && 'master' || github.ref }}
       os: ubuntu
-      dist: focal
+      dist: jammy
       submodule: ${{ inputs.submodule }}
       revision: ${{ inputs.revision }}