Remove robot plugin from palletizing world

[javizqh]

Remove

    <plugin filename="libgz_link_attacher.so" name="gz_link_attacher::LinkAttacher">
      <robot_model_name>ur10_suction</robot_model_name>
      <gripper_link_name>ls_vgr_link</gripper_link_name>
    </plugin>

And add it to the robot instead

[aroraanushri]

Hi, I’d like to work on this issue. I’ll reproduce and test the change before opening a PR.

[javizqh]

Feel free to do so following the contributor guidelines