Update mkdocs requirements

Author: mdmintz

docs/requirements.txt

@@ -1,11 +1,11 @@
-regex>=2020.10.28
+regex>=2020.11.11
 tqdm>=4.51.0
 livereload==2.6.3;python_version>="3.6"
 Markdown==3.3.3
 readme-renderer==28.0
 pymdown-extensions==8.0.1
 mkdocs==1.1.2
-mkdocs-material==6.1.0
+mkdocs-material==6.1.4
 mkdocs-simple-hooks==0.1.2
 mkdocs-material-extensions==1.0.1
 mkdocs-minify-plugin==0.3.0