Rounded Address Bar

### Describe the bug

The address bar isn't square-shaped/box-shaped like the tabs; the corners are rounded.

### Expected behavior

The corners shouldn't be rounded on the address bar.

### Screenshots

_No response_

### OS

Windows 10

### OS - Others

_No response_

### Firefox Version

146.0.1

### Distribution

- [ ] [Original Lepton](https://github.com/black7375/Firefox-UI-Fix)
- [x] [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
- [ ] Dark
- [ ] Alpenglow (System: Light)
- [ ] Alpenglow (System: Dark)
- [x] 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_

Reproduce the address bar appearance on Windows 10 with Firefox 146.0.1, using Lepton's photon style and the System Default theme. Inspect the address bar styling entry point and verify that its corners match the square shape of the tabs when done.

Written by the indexing model from the issue text.