Fix invalid metadata for 2.0 branch

[bact]

So this can be used with pip >= 24.1

Motivation

omegaconf 2.0 requirements/base.txt has this line:

PyYAML>=5.1.*

which is considered an invalid metadata for pip >= 24.1, and makes it unable to install.

Have you read the Contributing Guidelines on pull requests?

Yes

Test Plan

If it can be installed with pip install . (or pip install omegaconf>2.0.6 (please change the version number to fit), it should be considered a pass.

Fixes

By change that line in requirements/base.txt to:

PyYAML>=5.1.0

• This PR will fixes issue #1187
  • By fixing that issue, it will also help fixing https://github.com/facebookresearch/fairseq/issues/5436
  • fairseq 0.12.2 depends on omegaconf<2.1 hydra-core 1.0.7 depends on omegaconf<2.1 and >=2.0.5 https://github.com/facebookresearch/fairseq/pull/3722

[bact]

The checks failed at lint-3.6 with this message:

omegaconf/_utils.py:280: error: Returning Any from function declared to return "bool" Found 1 error in 1 file (checked 41 source files) nox > Session lint-3.6 failed.

The checks failed at lint-3.7 and lint-3.8 with this message:

ImportError while loading conftest '/home/circleci/project/tests/conftest.py'. tests/init.py:6: in import attr E ModuleNotFoundError: No module named 'attr' nox > Session coverage-3.8 failed. nox > Running session lint-3.8

Also in 3.7 and 3.8, there's an error with Jupyter notebook at the coverage check.

[bact]

Does there anything I should do more to improve this PR please? Thank you.