Fix BigModel stable diffusion pipeline (#19277)
### Description
Fix two issues:
(1) We can only use single quote inside `bash -c "..."`. Current
pipeline job stopped at `python3 demo_txt2img.py astronaut` and skip the
following commands. In this change, we remove the remaining commands to
get same effect (otherwise, the pipeline runtime might be 2 hours
instead of 15 minutes).
(2) Fix a typo of Stable.
