doc: kbuild: fix default in imply table

`BAZ` takes `FOO`'s value as default (as far as `BAR` allows it).

Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Author: ojeda

Documentation/kbuild/kconfig-language.rst

@@ -176,7 +176,7 @@ applicable everywhere (see syntax).
 	y		y		y		Y/m/n
 	n		m		n		N/m
 	m		m		m		M/n
-	y		m		n		M/n
+	y		m		m		M/n
 	y		n		*		N
 	===		===		=============	==============