Fix docs of database

beat/backend/python/database.py

@@ -88,8 +88,7 @@ class Runner(object):
 
       prefix (str): Establishes the prefix of your installation.
 
-      root_folder (str, path): The path pointing to the root folder of this
-        database
+      root_folder (str): The path pointing to the root folder of this database
 
       exc (:std:term:`class`): The class to use as base exception when
         translating the exception from the user code. Read the documention of