kconfig: drop 'boolean' keyword

No more users of this keyword.  Drop it according to the notice by
commit 6341e62b212a ("kconfig: use bool instead of boolean for type
definition attributes").

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Luis R. Rodriguez <mcgrof@kernel.org>
diff --git a/scripts/kconfig/mconf.c b/scripts/kconfig/mconf.c
index 315ce2c..c829be8b 100644
--- a/scripts/kconfig/mconf.c
+++ b/scripts/kconfig/mconf.c
@@ -246,7 +246,7 @@ search_help[] = N_(
 	"  Selected by: BAR [=n]\n"
 	"-----------------------------------------------------------------\n"
 	"o The line 'Type:' shows the type of the configuration option for\n"
-	"  this symbol (boolean, tristate, string, ...)\n"
+	"  this symbol (bool, tristate, string, ...)\n"
 	"o The line 'Prompt:' shows the text used in the menu structure for\n"
 	"  this symbol\n"
 	"o The 'Defined at' line tells at what file / line number the symbol\n"