ci: pin gitea runner image

Use the full ubuntu runner label so Gitea Actions resolves gitea/runner-images:ubuntu-22.04 instead of falling back to ubuntu:latest during test runs.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.gitea/workflows/package.yml

@@ -7,7 +7,7 @@ on:
 
 jobs:
   docker-image:
-    runs-on: ubuntu
+    runs-on: "ubuntu:docker://gitea/runner-images:ubuntu-22.04"
     permissions:
       contents: read
     defaults:
@@ -121,7 +121,7 @@ jobs:
             -d "{\"image\":\"${IMAGE_REF}\",\"tag\":\"${IMAGE_TAG}\",\"repo\":\"${REPOSITORY_PATH}\"}"
 
   deploy-fallback-log:
-    runs-on: ubuntu
+    runs-on: "ubuntu:docker://gitea/runner-images:ubuntu-22.04"
     needs: docker-image
     if: failure()
     steps: