lib: speech_recognition_slurm.sh renders unconditional --revision, unlike local template

[cswaney]

Surfaced during bot review of #518.

Context

The three speech-recognition launch templates handle `container_config.revision` inconsistently:

• speech_recognition_slurm.sh always emits `--revision {{ container_config.revision }}`, even when the value is empty/None.
• speech_recognition_local.sh wraps it in `{%- if container_config.revision %}` on both docker and apptainer branches, so an unset revision is simply omitted.

If `container_config.revision` is ever unset on the Slurm path, the rendered command would include `--revision` with an empty value. SRI 0.2.1's typer CLI accepts `--revision` as `Optional[str]`, so an empty string may or may not do the right thing depending on how the model store resolves it — worth confirming, but at minimum the Slurm template should behave like the local one.

Scope

• Confirm whether `container_config.revision` can be None/empty on the Slurm submission path (check `text_generation.py` / `speech_recognition.py` service builders and `asgi.py` request handling).
• If yes, wrap the flag in `{%- if container_config.revision %}` in `speech_recognition_slurm.sh` to match the local template.
• Consider whether `text_generation_slurm.sh` has the same shape (line 10 in the pre-chore(lib): bump speech-recognition-inference to 0.2.1 #518 tree) and needs the same treatment.