Refresh mkdocs dependencies

Author: mdmintz

mkdocs_build/requirements.txt

@@ -26,9 +26,9 @@ watchdog==2.1.9
 cairocffi==1.4.0
 cairosvg==2.5.2
 cssselect2==0.7.0
-tinycss2==1.1.1
+tinycss2==1.2.1
 defusedxml==0.7.1
-mkdocs==1.4.0
+mkdocs==1.4.1
 mkdocs-material==8.5.6
 mkdocs-exclude-search==0.6.4
 mkdocs-simple-hooks==0.1.5