Update dependency markdown to v3.9

| datasource | package  | from  | to  |
| ---------- | -------- | ----- | --- |
| pypi       | markdown | 3.8.2 | 3.9 |


Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

docs/requirements.txt

@@ -1,6 +1,6 @@
 mkdocs==1.6.1
 mike==2.1.3
-markdown==3.8.2
+markdown==3.9
 mkdocs-material==9.6.18
 
 # Markdown extensions