`infra/ci/requirements.txt` pins old PyYAML version that requires old Pythons

This came up on the Apache Arrow CI, where we validate that our development tree still builds properly on the OSS-Fuzz setup.

`infra/ci/requirements.txt` pins PyYAML to version 6.0.0, which is very old and doesn't install properly on Python 3.12+:
https://github.com/apache/arrow/issues/45059

It would probably be nice to bump the requirements to a more recent set of library versions.

(relatedly, it seems PyYAML isn't really being developed anymore)

Start with infra/ci/requirements.txt and inspect the PyYAML pin in the OSS-Fuzz CI setup. Update the dependency to a version that installs on Python 3.12 and newer, then verify that the OSS-Fuzz development-tree build succeeds with the revised requirements.

Written by the indexing model from the issue text.