Infra: Require Pygments 2.19 as a minimum (python#4730)

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
Co-authored-by: Michał Górny <mgorny@quansight.com>

Author: konstin

requirements.txt

@@ -1,5 +1,6 @@
 # Requirements for building PEPs with Sphinx
-Pygments >= 2.9.0
+# Sphinx requires >= 2.17. JSON5 support added in 2.19
+Pygments >= 2.19
 # Sphinx 6.1.0 broke copying images in parallel builds; fixed in 6.1.2
 # See https://github.com/sphinx-doc/sphinx/pull/11100
 Sphinx >= 5.1.1, != 6.1.0, != 6.1.1, < 8.1.0