Bump markdown2 from 2.4.2 to 2.4.3 (#656)

Bumps [markdown2](https://github.com/trentm/python-markdown2) from 2.4.2 to 2.4.3.
- [Release notes](https://github.com/trentm/python-markdown2/releases)
- [Changelog](https://github.com/trentm/python-markdown2/blob/master/CHANGES.md)
- [Commits](trentm/python-markdown2@2.4.2...2.4.3)

---
updated-dependencies:
- dependency-name: markdown2
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements.txt

@@ -14,7 +14,7 @@ lxml==4.8.0
 pytz==2021.3
 tzlocal==4.1
 libvirt-python==7.1.0; sys_platform != 'win32'
-markdown2==2.4.2
+markdown2==2.4.3
 flask-migrate==3.1.0
 flask-script==2.0.6
 email_validator