Fix wxChoice drop down height without visual theme in wxMSW

When using pre-v6 comctl32.dll (e.g. by disabling the visual styles
explicitly or by just not using the manifest), we need to update the
drop down height manually, and for this we must ensure that overridden
wxChoice::DoMoveWindow() is called from MSWUpdateDropDownHeight().

Closes #19026.

src/msw/choice.cpp

@@ -455,9 +455,18 @@ void wxChoice::MSWEndDeferWindowPos()
 
 void wxChoice::MSWUpdateDropDownHeight()
 {
+    int flags = wxSIZE_USE_EXISTING;
+    if ( wxApp::GetComCtl32Version() < 600 )
+    {
+        // Make sure our DoMoveWindow() will get called to update the dropdown
+        // height, this happens automatically with comctl32.dll v6, but not
+        // with earlier versions.
+        flags |= wxSIZE_FORCE;
+    }
+
     // be careful to not change the width here
     DoSetSize(wxDefaultCoord, wxDefaultCoord, wxDefaultCoord, GetSize().y,
-              wxSIZE_USE_EXISTING);
+              flags);
 }
 
 void wxChoice::DoMoveWindow(int x, int y, int width, int height)