Infra: Pin Pygments to a development version (#5024)

This allows the PEP 810 examples to be highlighted correctly. See also python/cpython#153227.

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Author: ZeroIntensity

requirements.txt

@@ -1,6 +1,10 @@
 # Requirements for building PEPs with Sphinx
+
 # Sphinx requires >= 2.17. JSON5 support added in 2.19
-Pygments >= 2.19
+# Temporary archive install, pending release of Pygments > 2.20.0
+# https://github.com/pygments/pygments/discussions/3145
+pygments @ git+https://github.com/pygments/pygments@2cad2642058441b59782a6a18f03c98c42d081f1
+
 # 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