tests: Remove extra TCH/HS puncturing value

3GPP TS 05.03 "Channel coding" specifies the puncturing matrix (1,0,1)
for class 1 information bits and tail bits valued u(0) to u(103) for a
maximum puncturing index of 311. The puncturing index 313 exceeds the
maximum index and causes osmo_conv_get_output_length() to output the
improper length of 210 instead of 211.

Signed-off-by: Thomas Tsou <tom@tsou.cc>