fix ROS<>LCM message converter for Unitree SDK v3.5.0

[k-okada]

To compile unitree_ros_to_real aginst unitree_legged_sdk v3.5.0 and above, unitreerobotics/unitree_legged_sdk@1cca3a3 breaks ToRos ToLcm functions.
This change fixes compile following compile error

boost_chrono -lboost_date_time -lboost_atomic -lpthread /usr/lib/x86_64-linux-gnu/libconsole_bridge.so.0.4 
[unitree_legged_real:make] make[2]: Leaving directory '/home/k-okada/catkin_ws/ws_unitree/build/unitree_legged_real'
[unitree_legged_real:make] [ 60%] Built target lcm_server                                                    
[unitree_legged_real:make] In file included from /home/k-okada/catkin_ws/ws_unitree/src/unitree_ros_to_real/unitree_legged_real/src/exe/velocity_mode.cpp:13:0:
[unitree_legged_real:make] /home/k-okada/catkin_ws/ws_unitree/src/unitree_ros_to_real/unitree_legged_real/include/convert.h: In function ‘unitree_legged_msgs::LowState ToRos(UNITREE_LEGGED_SDK::LowState&)’:
[unitree_legged_real:make] /home/k-okada/catkin_ws/ws_unitree/src/unitree_ros_to_real/unitree_legged_real/include/convert.h:108:27: error: ‘struct UNITREE_LEGGED_SDK::LowState’ has no member named ‘commVersion’; did you mean ‘version’?
[unitree_legged_real:make]      ros.commVersion = lcm.commVersion;
[unitree_legged_real:make]                            ^~~~~~~~~~~
[unitree_legged_real:make]                            version
[unitree_legged_real:make] /home/k-okada/catkin_ws/ws_unitree/src/unitree_ros_to_real/unitree_legged_real/include/convert.h:109:23: error: ‘struct UNITREE_LEGGED_SDK::LowState’ has no member named ‘robotID’
[unitree_legged_real:make]      ros.robotID = lcm.robotID;
[unitree_legged_real:make]                        ^~~~~~~
[unitree_legged_real:make] /home/k-okada/catkin_ws/ws_unitree/src/unitree_ros_to_real/unitree_legged_real/include/convert.h:110:18: error: cannot convert ‘std::array<unsigned int, 2>’ to ‘unitree_legged_msgs::LowState_<std::allocator<void> >::_SN_type {aka unsigned int}’ in assignment
[unitree_legged_real:make]      ros.SN = lcm.SN;
[unitree_legged_real:make]                   ^~
[unitree_legged_real:make] /home/k-okada/catkin_ws/ws_unitree/src/unitree_ros_to_real/unitree_legged_real/include/convert.h: In function ‘UNITREE_LEGGED_SDK::LowCmd ToLcm(unitree_legged_msgs::LowCmd&, UNITREE_LEGGED_SDK::LowCmd)’:
[unitree_legged_real:make] /home/k-okada/catkin_ws/ws_unitree/src/unitree_ros_to_real/unitree_legged_real/include/convert.h:134:9: error: ‘struct UNITREE_LEGGED_SDK::LowCmd’ has no member named ‘commVersion’; did you mean ‘version’?
[unitree_legged_real:make]      lcm.commVersion = ros.commVersion;
[unitree_legged_real:make]          ^~~~~~~~~~~
[unitree_legged_real:make]          version
[unitree_legged_real:make] /home/k-okada/catkin_ws/ws_unitree/src/unitree_ros_to_real/unitree_legged_real/include/convert.h:135:9: error: ‘struct UNITREE_LEGGED_SDK::LowCmd’ has no member named ‘robotID’
[unitree_legged_real:make]      lcm.robotID = ros.robotID;

[aaronsng]

What's wrong with this pull request? I think it works, shouldn't y'all fix this? Please merge thanks