Dark mode hover state on Community Toolkit SettingsExpander

### Describe the bug

Stroke on hover is the wrong color / border disappears on hover so there's no separation

### Regression

_No response_

### Reproducible in sample app?

- [ ] This bug can be reproduced in the sample app.

### Steps to reproduce

In dark mode, hover over Community Toolkit expander (while expanded) - notice the stroke thickness increase (and color) as well as the missing separation between parent expander and child item.

(Have not tested in sample app)

### Expected behavior

Separation between the parent expander and child item still exists while expander is being hovered on.

### Screenshots


### Windows Build Number

- [ ] Windows 10 1809 (Build 17763)
- [ ] Windows 10 1903 (Build 18362)
- [ ] Windows 10 1909 (Build 18363)
- [ ] Windows 10 2004 (Build 19041)
- [ ] Windows 10 20H2 (Build 19042)
- [ ] Windows 10 21H1 (Build 19043)
- [ ] Windows 11 21H2 (Build 22000)
- [ ] Other (specify)

### Other Windows Build number

_No response_

### App minimum and target SDK version

- [ ] Windows 10, version 1809 (Build 17763)
- [ ] Windows 10, version 1903 (Build 18362)
- [ ] Windows 10, version 1909 (Build 18363)
- [ ] Windows 10, version 2004 (Build 19041)
- [ ] Other (specify)

### Other SDK version

_No response_

### Visual Studio Version

_No response_

### Visual Studio Build Number

_No response_

### Device form factor

_No response_

### Nuget packages

_No response_

### Additional context

_No response_

### Help us help you

No.