gui_epicmenu.lua: hide hotkey for directory button

1) hide hotkey button for subdirectory button. 
Pro: In term of utility, hotkey is not needed for navigating menu & hiding hotkey make subdirectory button looked a bit different than regular button, 
Con: in term of aesthetic, the symmetry might be lesser because hotkey button does not appear on all button

2) Increase search result limit to 23. 
Pro: higher number will get result for vague search term
Con: higher number will mean more mix of button, checkbox & slider from all directory, will look messy.