[`SAM`] Change to `facebook/sam-vit-base`
# What does this PR do?

Changes the checkpoint name to `sam-vit-base` instead of `sam-vit-big` which was slightly confusing for users. The checkpoints are sorted with their size

- `sam-vit-base`: 350MB
- `sam-vit-large`: 1GB
- `sam-vit-huge`: 2GB

Which now makes more sense. The repo on the Hub have been updated accordingly

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