chore: switch workflow to ubuntu-latest

Author: computator

.github/workflows/main.yaml

@@ -8,7 +8,7 @@ on:
   workflow_dispatch:
 jobs:
   build:
-    runs-on: ubuntu-24.04 # uses podman from 24.04 or later
+    runs-on: ubuntu-latest
     env:
       REGISTRY: ghcr.io
       IMAGE: ghcr.io/${{ github.repository_owner }}/smtp-proxy