Increase scroll back cache size for desktop

### Your use case

#### What would you like to do?

Scroll up quickly without having to wait for unreliable servers when the clients been open the whole time.

#### Why would you like to do it?
Matrix servers are unreliable.

#### How would you like to achieve it?
Increase the chat scroll up buffer, modern desktops have tons of ram/disk space after all.

### Have you considered any alternatives?

_No response_

### Additional context

_No response_