Update requirements.txt

Author: AA-Turner

requirements.txt

@@ -1,5 +1,6 @@
 # Requirements for building PEPs with Sphinx
-Pygments >= 2.19.0
+# 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