fix(ci): remove container directive from Gitea workflows for host-mode runner

The bezalel-vps-runner is registered in host mode (:host labels)
and cannot execute Docker containers. The container pinning added
in #180 causes all Gitea CI jobs to fail immediately with:

  Cannot connect to the Docker daemon at unix:///var/run/docker.sock

Remove container: from .gitea/workflows/*.yml while keeping it in
.github/workflows/ for actual GitHub Actions runners.

Fixes CI for all open PRs and main branch pushes.

.gitea/workflows/ci.yml

@@ -13,7 +13,6 @@ concurrency:
 jobs:
   smoke-and-build:
     runs-on: ubuntu-latest
-    container: catthehacker/ubuntu:act-22.04
     timeout-minutes: 5
     steps:
       - name: Checkout code

.gitea/workflows/notebook-ci.yml

@@ -11,7 +11,6 @@ on:
 jobs:
   notebook-smoke:
     runs-on: ubuntu-latest
-    container: catthehacker/ubuntu:act-22.04
     steps:
       - name: Checkout
         uses: actions/checkout@v4