Fix dropdown showing in up direction (#10009)

## Summary of the Pull Request
Let the dropdown menu open downwards if there's enough space, when clicking on the down arrow.

## PR Checklist
* [X] Closes #8924 
* [X] CLA signed.

## Detailed Description of the Pull Request / Additional comments
Set the placement of the flyout to BottomEdgeAlignedLeft, as was done when opening the menu from the key binding.

## Validation Steps Performed
Manual tests

src/cascadia/TerminalApp/TerminalPage.cpp

@@ -524,6 +524,8 @@ namespace winrt::TerminalApp::implementation
     void TerminalPage::_CreateNewTabFlyout()
     {
         auto newTabFlyout = WUX::Controls::MenuFlyout{};
+        newTabFlyout.Placement(WUX::Controls::Primitives::FlyoutPlacementMode::BottomEdgeAlignedLeft);
+
         auto keyBindings = _settings.KeyMap();
 
         const auto defaultProfileGuid = _settings.GlobalSettings().DefaultProfile();
@@ -713,13 +715,10 @@ namespace winrt::TerminalApp::implementation
 
     // Function Description:
     // Called when the openNewTabDropdown keybinding is used.
-    // Adds the flyout show option to left-align the dropdown with the split button.
     // Shows the dropdown flyout.
     void TerminalPage::_OpenNewTabDropdown()
     {
-        WUX::Controls::Primitives::FlyoutShowOptions options{};
-        options.Placement(WUX::Controls::Primitives::FlyoutPlacementMode::BottomEdgeAlignedLeft);
-        _newTabButton.Flyout().ShowAt(_newTabButton, options);
+        _newTabButton.Flyout().ShowAt(_newTabButton);
     }
 
     winrt::fire_and_forget TerminalPage::_RemoveOnCloseRoutine(Microsoft::UI::Xaml::Controls::TabViewItem tabViewItem, winrt::com_ptr<TerminalPage> page)