Grey tab bar after updating to 146.0

### Describe the bug

I did `git pull` and cleared startup cache, which usually resolves this issue, but ig not this time.

### Expected behavior

_No response_

### Screenshots

### OS

Windows 11

### OS - Others

_No response_

### Firefox Version

146.0

### Distribution

- [x] [Original Lepton](https://github.com/black7375/Firefox-UI-Fix)
- [ ] [Lepton's photon style](https://github.com/black7375/Firefox-UI-Fix/tree/photon-style)
- [ ] [Lepton's proton style](https://github.com/black7375/Firefox-UI-Fix/tree/proton-style)

### Theme

- [ ] Light
- [x] Dark
- [ ] Alpenglow (System: Light)
- [ ] Alpenglow (System: Dark)
- [ ] System Default
- [ ] Others: (e.g. [Photon Colors](https://addons.mozilla.org/en-US/firefox/addon/photon-colors/), [Google Chrome Dark](https://addons.mozilla.org/en-US/firefox/addon/google-chrome-dark/), [Fairytale Of Nature](https://addons.mozilla.org/en-US/firefox/addon/fairytale-of-nature/))

### Theme - More Info

_No response_

### `user.js` setup

user.js setup

```javascript
// Your settings
```

### Additional context

_No response_

Start by reproducing the grey tab bar on Windows 11 with Firefox 146.0, using the Original Lepton distribution and dark theme after clearing startup cache. Compare the affected tab-bar styles with the previous Firefox version; done means the tab bar displays normally after updating.

Written by the indexing model from the issue text.