Consider removing historical profile

### Description

When a person changes their nickname or profile picture, this isn't reflected in older messages they typed. Instead, all messages in the backlog up to the time of change use the old ones.

### Steps to reproduce

- Have a chat with a person
- Have that person rename or change profile picture
- Scroll through the backlog

Logs being sent: no

### Version information

- **Platform**: web

For the web app:

- **Browser**: Chromium
- **OS**: Arch Linux
- **URL**: app.element.io