Element is spamming my homeserver with invalid requests

### Description

Trying to open a forgotten room sends the client into a loop of trying to request messages from the homeserver and it returning 403.

### Steps to reproduce

- Join a channel
- Leave it
- Forget it
- Open dev console to see network requests
- Try to click on the forgotten channel under "Historical"
- Watch as the dev console shows many 403 errors with the content string `{"errcode":"M_FORBIDDEN","error":"user already forgot about this room"}`

### Screenshot / debug logs


Github doesn't allow me to upload `.tar` files here, so I uploaded the rageshake.tar that Element gave me to 0x0: https://0x0.st/-p9N.tar

### Version information

- OS: PopOS 20.04 LTS
- Element version: 1.7.31