chore: remove inference code, add pt framework.
To keep it consistent with the other docs ([image classification](https://huggingface.co/docs/transformers/tasks/image_classification), [audio classification](https://huggingface.co/docs/transformers/tasks/audio_classification), etc.), this PR:

* removes inference code 
* adds separation for PT as a framework 

in the [semantic segmentation](https://huggingface.co/docs/transformers/tasks/semantic_segmentation) guide. 
_The documentation is not available anymore as the PR was closed or merged._<|||||>Sorry, I missed that PR. I thought this was outside the scope of task guides. Sounds good to not go ahead with this change. Let's still add the pt framework block<|||||>Agreed. 