chore(ci): drop transient smoke workflow now that runner is validated

The smoke workflow was scoped from inception to validate that the
freshly registered gitea-runner picks up jobs with the "linux" label.
It ran green on push of chore/podman-and-ci. Removing per the
"transient, removed after validation" plan recorded in the original
commit (1380672).

.gitea/workflows/smoke.yml

@@ -1,22 +0,0 @@
-name: smoke
-# Trivial workflow to validate the Gitea Actions runner pickup.
-# Removed in a follow-up commit once green on chore/podman-and-ci.
-
-on:
-  push:
-    branches:
-      - chore/podman-and-ci
-  workflow_dispatch:
-
-jobs:
-  hello:
-    runs-on: linux
-    steps:
-      - name: kernel + identity
-        run: |
-          echo "host: $(uname -a)"
-          id
-          cat /etc/os-release | head -3
-      - name: container runtime visible from job
-        run: |
-          which podman || which docker || echo "(no runtime visible — expected for nested rootless DooD)"