[3.12] Docs: bump Pygments to fix contrast ratios to meet WCAG AA guidelines (GH-110208) (#110210)

Docs: bump Pygments to fix contrast ratios to meet WCAG AA guidelines (GH-110208)
(cherry picked from commit 9cb8927)

Co-authored-by: Hugo van Kemenade <[email protected]>

Author: miss-islington

Doc/constraints.txt

@@ -10,8 +10,7 @@ colorama<0.5
 imagesize<1.5
 Jinja2<3.2
 packaging<24
-# Pygments==2.15.0 breaks CI
-Pygments<2.16,!=2.15.0
+Pygments>=2.16.1,<3
 requests<3
 snowballstemmer<3
 sphinxcontrib-applehelp<1.1