Refresh mkdocs dependencies

Author: mdmintz

mkdocs_build/requirements.txt

@@ -22,7 +22,7 @@ jsmin==3.0.1
 lunr==0.6.2
 nltk==3.7
 tornado==6.2
-watchdog==2.1.9
+watchdog==2.2.0
 cairocffi==1.4.0
 cairosvg==2.5.2
 cssselect2==0.7.0