build(deps): update markdownify requirement from ~=0.12.1 to ~=0.13.1

Updates the requirements on [markdownify](https://github.com/matthewwithanm/python-markdownify) to permit the latest version.
- [Release notes](https://github.com/matthewwithanm/python-markdownify/releases)
- [Commits](matthewwithanm/python-markdownify@0.12.1...0.13.1)

---
updated-dependencies:
- dependency-name: markdownify
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -2,7 +2,7 @@ discord.py~=2.4.0
 feedparser~=6.0.11
 gspread~=6.1.2
 jishaku~=2.5.2
-markdownify~=0.12.1
+markdownify~=0.13.1
 psutil~=6.0.0
 pytz~=2024.1
 rapidfuzz>=3.0.0,<4.0.0