fix(actions): exclude `workflow_call` from workflow trigger detection (#37894)

Gitea now only allows `workflow_dispatch.inputs`. If a workflow contains
`workflow_call.inputs`, the workflow cannot be triggered, even though
the `on:` section contains other trigger events.


https://github.com/go-gitea/gitea/blob/428ee9fcce7928bf5405900345d43e9ba1b01564/modules/actions/jobparser/model.go#L402-L405

For example, this workflow cannot be triggered due to
`workflow_call.inputs`:
```yaml
on:
  push:
  pull_request:
  workflow_call:
    inputs:
      name:
        type: string
```

---

This PR is extracted from #37478 for backport

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.8) <noreply@anthropic.com>
Co-authored-by: Giteabot <teabot@gitea.io>