feat: update the framework lesson of the JS2 course to be about JavaScript (#1847)

Part of #1584

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⚠️ 🐍 This PR contains also changes to the Python course, to keep the
lessons consistent and synced.

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Co-authored-by: Michał Olender <[email protected]>
Co-authored-by: gullmar <[email protected]>

Author: 3 people