How to delete all comments and notes in the spreadsheet
There are several different ways how to delete all comments in your spreadsheet quickly, but the fastest and easiest is to:
1. Select all cells in your spreadsheet. For example, by clicking Ctrl+A (see also Quick way to select all cells for more details).
2. On the Review tab, in the Comments group, click the Delete button:

See also this tip in French: Comment supprimer tous les commentaires dans la feuille de calcul.