Room list entries have poor colour contrast

### Steps to reproduce

1. Join some rooms
2. View the room list in light mode

### Outcome

#### What did you expect?

The room list entries should have sufficient colour contrast. (Previously, they were `#000000` on `#FFFFFF`, with a WCAG AAA compliant contrast ratio of 21:1.)

#### What happened instead?

Room list entries for rooms with no unread messages are (seemingly as of #32421) `#656D77` on `#FFFFFF`, with a contrast ratio of 5.24:1, failing WCAG AAA recommendations.

### Operating system

_No response_

### Browser information

Firefox 148.0b3

### URL for webapp

staging.element.io

### Application version

Element version: 1.12.11-rc.1

### Homeserver

_No response_

### Will you send logs?

No