acceptance-tests.yml: Upgrade workflow from unsupported platform

Ubuntu 20.04 LTS reached its EOL in April 2025. Upgraded platform to
Ubuntu 22.04 LTS.

Signed-off-by: Lars Erik Wik <[email protected]>

Author: larsewi

.github/workflows/acceptance_tests.yml

@@ -5,7 +5,7 @@ on:
 
 jobs:
   acceptance_tests:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
     - uses: actions/checkout@v3
       with: