docs: bump pygments from 2.18.0 to 2.19.2

[nikpivkin]

Description

This PR upgrades pygments using the command:
pip-compile --upgrade-package pygments --output-file=docs/build/requirements.txt docs/build/requirements.in

Pygments versions starting from 2.19.0 add support for Rego syntax highlighting.

Before:

After:

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).