Update datasets requirement from <2.20,>=2.19 to >=2.20.0,<2.21

Updates the requirements on [datasets](https://github.com/huggingface/datasets) to permit the latest version.
- [Release notes](https://github.com/huggingface/datasets/releases)
- [Commits](huggingface/datasets@2.19.0...2.20.0)

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

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

setup.py

@@ -60,7 +60,7 @@
     'transformers>=4.42.3,<4.43',
     'mosaicml-streaming>=0.7.6,<0.8',
     'torch>=2.3.0,<2.4',
-    'datasets>=2.19,<2.20',
+    'datasets>=2.20.0,<2.21',
     'fsspec==2023.6.0',  # newer version results in a bug in datasets that duplicates data
     'sentencepiece==0.1.97',
     'einops==0.7.0',