Update course description to include ENSAI

[jpramil]

Added ENSAI to the course description for clarity.

Description

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Checklist

• I have read the contribution guidelines:
  • French: https://github.com/linogaliana/python-datascientist/blob/main/doc/CONTRIBUTING-fr.md
  • English: https://github.com/linogaliana/python-datascientist/blob/main/doc/CONTRIBUTING-en.md
• If this is a substantial change, I have opened an issue to discuss it.
• I have followed the contribution rules described in the documentation.
• I have added or updated tests if needed.
• I have updated the documentation if needed.

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Additional information

Add any extra context, issues this PR closes, or points that need review.