* Fix memory leak in base_class.py
Loading the data return value is not necessary since it is unused. Loading the data causes a memory leak through the ep_info_buffer variable. I found this while loading a PPO learner from storage on a multi-GPU system since the ep_info_buffer is loaded to the memory location it was on while it was saved to disk, instead of the target loading location, and is then not cleaned up.
* Update changelog.rst
* Update changelog
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Co-authored-by: Antonin RAFFIN <antonin.raffin@ensta.org>