Add missing word in polish.lua (#24)

lua/polish.lua

@@ -1,7 +1,7 @@
 if true then return end -- WARN: REMOVE THIS LINE TO ACTIVATE THIS FILE
 
 -- This will run last in the setup process and is a good place to configure
--- things like custom filetypes. This just pure lua so anything that doesn't
+-- things like custom filetypes. This is just pure lua so anything that doesn't
 -- fit in the normal config locations above can go here
 
 -- Set up custom filetypes