kconfig: remove unused definition from scanner

The definition ws [ \n\t] is not used anywhere. Drop it to avoid confusion.

As it is a dead definition, any changes in the resulting code generated by
flex would be surprising (actually testing this showed that there are really
no changes). So, there is no need to touch the existing zconf.lex.c_shipped.

Signed-off-by: Martin Walch <walch.martin@web.de>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: "Yann E. MORIN: <yann.morin.1998@free.fr>