Documentation/kconfig: more concise and straightforward search explanation

Re-phrase the explanations on the sorting of search results, in a more
concise and complete way.

Drop reference to the user's locale when sorting alphabetically, since
this is implicit.

Reported-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Jean Delvare <jdelvare@suse.de>
Reviewed-by: Jean Delvare <jdelvare@suse.de>