Bump markdown from 3.6 to 3.7

Bumps [markdown](https://github.com/Python-Markdown/markdown) from 3.6 to 3.7.
- [Release notes](https://github.com/Python-Markdown/markdown/releases)
- [Changelog](https://github.com/Python-Markdown/markdown/blob/master/docs/changelog.md)
- [Commits](Python-Markdown/markdown@3.6...3.7)

---
updated-dependencies:
- dependency-name: markdown
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

requirements.txt

@@ -6,7 +6,7 @@ colorama==0.4.6
 ghp-import==2.1.0
 idna==3.7
 Jinja2==3.1.4
-Markdown==3.6
+Markdown==3.7
 markdown-callouts==0.4.0
 MarkupSafe==2.1.5
 mergedeep==1.3.4