tc_util: No need to terminate an snprintf'ed buffer

snprintf() won't leave the buffer unterminated, so manually terminating
is not necessary here.

Signed-off-by: Phil Sutter <phil@nwl.cc>

tc/tc_util.c

@@ -434,7 +434,6 @@ static const char *action_n2a(int action)
 		return "trap";
 	default:
 		snprintf(buf, 64, "%d", action);
-		buf[63] = '\0';
 		return buf;
 	}
 }