Working around compilation error with NVC.

Author: LarsAsplund

vunit/vhdl/data_types/test/tb_codec.vhd

@@ -21,8 +21,6 @@ library ieee;
 use ieee.std_logic_1164.all;
 use ieee.math_complex.all;
 use ieee.math_real.all;
-use ieee.numeric_bit.all;
-use ieee.numeric_std.all;
 
 use std.textio.all;