DropDownButton menu does not change from dark mode to light mode

[chenss3]

Describe the bug

When the app is still running and you change from light mode to dark mode (or from dark to light), the DropDownButton menu color mode will not change.

This is seen in the WinUI 3 gallery app or a blank WinUI 3 app that uses the control.

Steps to reproduce the bug

1. Start in dark mode
2. Go to WinUI3 Gallery to the DropDownButton control (or create a blank WinUI 3 app and add a DropDownButton control)
3. Change theme mode to light mode in the settings app
4. DropDownButton menu will continue to be dark.

It does the same problem when you go from light mode to dark mode too (the menu will continue being light mode while the rest of the app and button is dark mode).

Expected behavior

When changing from dark to light mode, I expect the menu to change to light mode as well.

Screenshots

NuGet package version

None

Windows version

Windows Insider Build (xxxxx)

Additional context

No response