Pin setuptools to fix Docker build error

See [this Issue](https://github.com/IDEA-Research/Grounded-SAM-2/issues/98). The Dockerfile is broken since a recent update to setuptools and pip, which disables the option to load packages from within setup.py. See [this issue](https://github.com/facebookresearch/sam2/issues/611#issuecomment-2741690522) in the original sam2 repo, and [this PR](https://github.com/IDEA-Research/Grounded-SAM-2/pull/91) in this repo.