Updated paths to preferences.txt in manpage

Fix #6061

Author: cmaglie

build/shared/manpage.adoc

@@ -212,7 +212,9 @@ EXIT STATUS
 
 FILES
 -----
-*~/.arduino15/preferences.txt*::
+*%LOCALAPPDATA%/Arduino15/preferences.txt* (Windows)::
+*~/Library/Arduino15/preferences.txt* (Max OS X)::
+*~/.arduino15/preferences.txt* (Linux)::
 	This file stores the preferences used for the IDE, building and
 	uploading sketches.