Background of emoji suggestion bar in message composer is transparent

### Steps to reproduce

As reported by another user. Rageshake has been linked.

I'm unable to reproduce myself, even in Firefox on app.element.io.

### Outcome

#### What did you expect?

The background of the message composer emoji picker to be opaque, so emoji names can easily be read.

#### What happened instead?

It was transparent.

### Operating system

Linux

### Browser information

Firefox 147.0

### URL for webapp

_No response_

### Application version

1 2 Version von Element: 1.12.9 Krypto-Version: Rust SDK 0.16.0 (95b5e83), Vodozemac 0.9.0

### Homeserver

N/A

### Will you send logs?

Yes