Back-paginating the threads panel loads rooms in entirely the wrong order

### Steps to reproduce

1. Try to find an old threads
2. Scroll back through the thread panel
3. Discover that the threads are not ordered chronologically. I have:
* Nov 20th 2023 -> Oct 20th 2023
* Jan 18th 2024 -> Nov 21st 2023
* Jan 19th 2024 -> Feb 16th 2024
* one thread at the bottom from Jan 5th 2024

i.e. 4 different blocks; two ordered reverse chronological; the third ordered fwd chronological; and one spurious one (which might have been a search result?)

### Outcome

#### What did you expect?

Consistent ordering of the thread panel

#### What happened instead?

Paginated chunks ordered in the wrong direction.

### Operating system

_No response_

### Browser information

_No response_

### URL for webapp

_No response_

### Application version

nightly

### Homeserver

matrix.org

### Will you send logs?

No