libgazebo_yarp_worldinterface contained in left_wrist_mk2 and left_hand_mk3

[traversaro]

While working on another issue, I noticed that the models left_wrist_mk2 and left_hand_mk3 internally spawn as libgazebo_yarp_worldinterface plugin. As this plugin is not intended to be part of a model, but rather to be spawned as part of a specific world used for some experiments, do you think we can remove it?

@ale-git @xEnVrE @gabrielecaddeo