fix(docs): Pin pymdown-extensions to v12.1 (#23386)

pymdown-extensions v12.2 made `md` a required argument of
`pymdownx.highlight.Highlight.__init__()`, which mkdocstrings v1.0.6 does
not pass, breaking `zensical build`. Pin to v12.1 until mkdocstrings is
compatible.

Closes: #23385

base_requirements.txt

@@ -133,6 +133,11 @@ Pillow
 # https://github.com/psycopg/psycopg/blob/master/docs/news.rst
 psycopg[c,pool]
 
+# Markdown extensions (for documentation build)
+# Pinned below v12.2 pending mkdocstrings compatibility (see #23385)
+# https://github.com/facelessuser/pymdown-extensions/releases
+pymdown-extensions<12.2
+
 # YAML rendering library
 # https://github.com/yaml/pyyaml/blob/master/CHANGES
 PyYAML

requirements.txt

@@ -30,6 +30,7 @@ netaddr==1.3.0
 nh3==0.3.7
 Pillow==12.3.0
 psycopg[c,pool]==3.3.6
+pymdown-extensions==12.1
 PyYAML==6.0.3
 redis==8.1.0
 requests==2.34.2