[Week04] Migrate to gymnasium

[laktionov]

• Support new interfaces in all files and notebooks
• Change done to terminated or truncated to iterate over env
• Add comment regarding done value for the replay buffer:

Whenever game ends due to termination or truncation, add record with done=terminated and reset the game.

• Update video recording code

[review-notebook-app[bot]]

Check out this pull request on 

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[dniku]

Thanks!