Update pymongo requirement comment for more modules that use it

requirements.txt

@@ -12,7 +12,8 @@ python-simple-hipchat==0.2
 prettytable==0.7.2
 awscli==1.4.2
 requests
-# Needed for the mongo_status module(playbooks/library/mongo_status)
+
+# Needed for the mongo_* modules (playbooks/library/mongo_*)
 pymongo==3.1
 
 # Needed for the mysql_db module