The button "Pick a Scope" doesn't highlight in the High Contrast themes when the mouse hovers on it

**OS:** Win11
**Build Version:** 0.26.54

**Repro Steps:**

1. Select "Light High Contrast" theme.
2. Create a [main.zip](https://github.com/Azure/bicep/files/14919138/main.zip) file with the following and open it in VSCODE.
3. Right click the file -> Click "Show Deployment Pane to the Side".
4. The mouse hovers on the button "Pick a Scope".
5. Check whether the button "Pick a Scope" highlights.

**Expect:**
The button "Pick a Scope" highlights.

**Actual:**
The button "Pick a Scope" doesn't highlight.

**More Info:**
This issue also reproduces in "Dark High Contrast" theme.

Reproduce the issue in Light High Contrast and Dark High Contrast themes by opening the deployment pane through “Show Deployment Pane to the Side” and hovering over “Pick a Scope.” Trace the pane’s UI styling from that entry point; done means the button highlights on hover in both themes.

Written by the indexing model from the issue text.