disable gradients

Potential runtime implications at

https://github.com/lbr-stack/ros2_roboreg/blob/ccec92ade8d308614ca07a1386ec4e8cda748403/ros2_roboreg/ros2_roboreg/plugins/render.py#L11

add torch no grad decorator or similar

Might be better added at on render callback

https://github.com/lbr-stack/ros2_roboreg/blob/ccec92ade8d308614ca07a1386ec4e8cda748403/ros2_roboreg/ros2_roboreg/reg/base.py#L462