Fixed loading correct ur macro depending if it is simulation or real …

[LokneyRobotnik]

…robot

[robert-ros]

After reviewing this, I found that this fix is not actually required because the changes introduced in #88 are already correct for both real robots and simulation.

In that PR, in ur_macro.xacro, ur_description was replaced with ur_simulation_gz. This change is only relevant for simulation and is required to support newer versions of the Universal Robots simulation packages. It does not affect real robots.

This PR proposes introducing two macros: keeping ur_macro for real robots and adding ur_macro_sim for simulation. However, for real robots, both macros are effectively identical.

The only meaningful difference appears in simulation. When setting the control file, ur_macro still references ur_description, which is deprecated, while ur_macro_sim uses ur_simulation_gz, which is the correct package to use going forward.

Therefore, the correct solution is to update ur_macro so that it matches the implementation of ur_macro_sim. After testing and comparing both implementations, it turns out that this change was already introduced in PR #88. Consequently, the issue is already addressed, and no further changes are necessary.

[LokneyRobotnik]

Hi!
As long robotnik_description package works correctly with real robot and simulation without need for separate macros, I am fine with this solution.