[`SAM`] Fixes pipeline and adds a dummy pipeline test
# What does this PR do?

1- Fixes the automatic mask generation pipeline, currently on the main branch, the script below

```python
from transformers import pipeline
from PIL import Image
import requests

generator = pipeline("mask-generation", model="facebook/sam-vit-base", device=0)

img_url = "https://huggingface.co/datasets/huggingface/documentation-images/resolve/main/transformers/tasks/car.jpg"
raw_image = Image.open(requests.get(img_url, stream=True).raw).convert("RGB")

outputs = generator(raw_image, points_per_batch=64)
```
is broken

2- Adds a dummy pipeline test. I know the pipelines are already tested in tests/pipeline but these tests are quite slow. I thought adding a small dummy pipeline test is easier for future contributors to make sure they will not break the pipeline without having to run the entire pipeline testing suite for SAM


cc @ArthurZucker @ydshieh @sgugger 
_The documentation is not available anymore as the PR was closed or merged._