Update dependency Markdown to v3.4.4 (#484)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [Markdown](https://togithub.com/Python-Markdown/markdown)
([changelog](https://togithub.com/Python-Markdown/markdown/blob/master/docs/change_log/index.md))
| patch | `==3.4.3` -> `==3.4.4` |

---

### Release Notes

<details>
<summary>Python-Markdown/markdown</summary>

###
[`v3.4.4`](https://togithub.com/Python-Markdown/markdown/compare/3.4.3...3.4.4)

[Compare
Source](https://togithub.com/Python-Markdown/markdown/compare/3.4.3...3.4.4)

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined),
Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you
are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update
again.

---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, click
this checkbox.

---

This PR has been generated by [Renovate
Bot](https://togithub.com/renovatebot/renovate).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzMi4xOTAuNiIsInVwZGF0ZWRJblZlciI6IjMyLjE5MC42In0=-->

.github/workflows/mkdocs-requirements.txt

@@ -3,7 +3,7 @@ future==0.18.3
 Jinja2==3.1.2
 livereload==2.6.3
 lunr==0.6.2
-Markdown==3.4.3
+Markdown==3.4.4
 MarkupSafe==2.1.3
 mkdocs==1.4.3
 mkdocs-macros-plugin==1.0.2