Top white line at Dock pinned to bottom in Dark Mode

### Microsoft PowerToys version

v0.100.2

### Installation method

Microsoft Store

### Area(s) with issue?

Command Palette

### Steps to reproduce

I pinned dock to bottom. When it changed from light to dark theme, then I can see ultra wide line on top of it.

### ✔️ Expected Behavior

Remove this white line, or replace with more discreet tone. Look at system task bar with dimmed border.

### ❌ Actual Behavior

Cruel white line on the top of the Dock in dark mode

### Upload Bug Report ZIP-file

_No response_

### Additional Information

Win 11

### Other Software

_No response_

Reproduce the Command Palette dock pinned to the bottom, then switch from light to dark mode on Windows 11 and inspect the bright top line shown in the report. No file or test is named, so first locate the dock's theme and border rendering entry point; done means the line is removed or uses a subdued dark-mode tone without changing the surrounding taskbar appearance.

Written by the indexing model from the issue text.