Review: pandas_panel.md

Part of #40 (Phase 1).

Native-speaker review of pandas_panel.md by @Honaminto.

How to reply. Open a PR editing the French directly — one PR for this lecture, titled e.g. [pandas_panel] Corrections — or leave line comments / suggestion blocks on it. Priorities: meaning errors, wrong technical terms, inconsistent terminology, unnatural French (academic register), anything in code comments that looks wrong. Ignore spacing before : ; ! ?, errors in the English, and the translation: header. A wrong term that recurs belongs on the terminology issue, not here.

Done when a PR by @Honaminto touching this file is merged, or he states here that the lecture needs no change. Either outcome is recorded; nothing is ticked by hand.

Ouvrir lectures/pandas_panel.md dans le dépôt français et le comparer avec la source anglaise liée. Vérifier le sens, les termes techniques, la cohérence terminologique, le français académique et les commentaires du code, tout en respectant les exclusions indiquées. La tâche est considérée comme terminée lorsqu’un PR de @Honaminto modifiant ce fichier est fusionné, ou lorsqu’il confirme qu’aucune modification n’est nécessaire.