Bump markdown2 from 2.3.8 to 2.4.0 in /web/notes

Bumps [markdown2](https://github.com/trentm/python-markdown2) from 2.3.8 to 2.4.0.
- [Release notes](https://github.com/trentm/python-markdown2/releases)
- [Changelog](https://github.com/trentm/python-markdown2/blob/master/CHANGES.md)
- [Commits](trentm/python-markdown2@2.3.8...2.4.0)

---
updated-dependencies:
- dependency-name: markdown2
  dependency-type: direct:production
...

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

Author: dependabot[bot]

web/notes/requirements.txt

@@ -14,7 +14,7 @@ itsdangerous==1.1.0
 Jinja2==2.11.1
 jsmin==2.2.2
 lesscpy==0.13.0
-markdown2==2.3.8
+markdown2==2.4.0
 MarkupSafe==1.1.1
 ply==3.11
 psutil==5.7.0