Make kelp not pass light (#4869)

the base blocks are solid, and should not pass light.

Fixes: light on sea floor with a mineshaft underneath.

Reviewed-on: https://git.minetest.land/VoxeLibre/VoxeLibre/pulls/4869
Reviewed-by: Mikita Wiśniewski <rudzik8@protonmail.com>
Co-authored-by: kno10 <erich.schubert@gmail.com>
Co-committed-by: kno10 <erich.schubert@gmail.com>

mods/ITEMS/mcl_ocean/kelp.lua

@@ -526,7 +526,7 @@ kelp.registered_surfaces = {}
 -- If you define your own properties, it overrides the default ones.
 kelp.surface_deftemplate = {
 	drawtype = "plantlike_rooted",
-	paramtype = "light",
+	paramtype = "none",
 	paramtype2 = "leveled",
 	place_param2 = 16,
 	--tiles = def.tiles,