gha: add ubuntu-22.04 to matrix

Signed-off-by: Aleksa Sarai <[email protected]>

Author: cyphar

.github/workflows/ci.yml

@@ -122,6 +122,13 @@ jobs:
           - "1.21"
           - "oldstable"
           - "stable"
+        include:
+          # Make sure we test with a slightly older kernel (sadly we can't use
+          # really old images like Ubuntu 18.04). Ubuntu 22.04 uses Linux 6.8.
+          - os: ubuntu-22.04
+            go-version: "oldstable"
+          - os: ubuntu-22.04
+            go-version: "stable"
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4