Update dependency Markdown to v3.4.3 (#33)

Co-authored-by: Zac Sweers <[email protected]>

.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==3.3.7
+Markdown==3.4.3
 MarkupSafe==2.1.2
 mkdocs==1.4.2
 mkdocs-macros-plugin==0.7.0