[SECURITY] Fix huge security flaw

[Z3rio]

Description

This PR removes the event called qb-inventory:server:SaveStashItems. Which is used to update the items of any stash that exists in QBCore. There is also no base qb-core script that even uses this event, making it useless to still have this.

Checklist

• [x] I have personally loaded this code into an updated qbcore project and checked all of its functionality.
• [x] My code fits the style guidelines.
• [x] My PR fits the contribution guidelines.