fix: Corrected adder code snippet in behavioral lab (#23)

chapters/verilog/behavioral/reading/README.md

@@ -113,6 +113,7 @@ module my_module(
  for (i = 0; i < 4; i = i + 1) begin
  {c, o[i]} = a[i] + b[i] + c;
  end
+ o[4] = c;
  end
 endmodule
 ```