Update the rest of the blast resistance values

The values have been updated according to this list:

https://minecraft.gamepedia.com/Module:Blast_resistance_values

mods/ITEMS/mcl_signs/init.lua

@@ -412,7 +412,7 @@ minetest.register_node("mcl_signs:wall_sign", {
 		end
 	end,
 	_mcl_hardness = 1,
-	_mcl_blast_resistance = 5,
+	_mcl_blast_resistance = 1,
 })
 
 -- Standing sign nodes.
@@ -452,7 +452,7 @@ local ssign = {
 	end,
 
 	_mcl_hardness = 1,
-	_mcl_blast_resistance = 5,
+	_mcl_blast_resistance = 1,
 }
 
 minetest.register_node("mcl_signs:standing_sign", ssign)