Update transformers requirement from <4.20,>=4.1 to >=4.1,<4.21 (#5675)
Update transformers requirement from <4.20,>=4.1 to >=4.1,<4.21 (#5675)

Updates the requirements on [transformers](https://github.com/huggingface/transformers) to permit the latest version.
- [Release notes](https://github.com/huggingface/transformers/releases)
- [Commits](https://github.com/huggingface/transformers/compare/v4.1.0...v4.20.0)

---
updated-dependencies:
- dependency-name: transformers
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>

Co-authored-by: dependabot[bot] <1c358da00a777d4e9898c1280ab801e2df165188@users.noreply.github.com>
Co-authored-by: Akshita Bhagia <fd26d827fa0372727e3d5ee90ef2583b0c2ed56a@gmail.com>
Co-authored-by: Pete <8aa1dcec45eed2823433bd3f497ad7c510fe0357@gmail.com>
allenai/allennlp,allenai/allennlp,allenai/allennlp,allenai/allennlp