Hardcode minimal widget sample notebook size

Not doing this resulted in the window being tiny by default, so it's
better than nothing, even if it's clearly still not ideal.

See #24154.

samples/widgets/widgets.cpp

@@ -506,8 +506,9 @@ WidgetsFrame::WidgetsFrame(const wxString& title)
     // Uncomment to suppress page theme (draw in solid colour)
     //style |= wxNB_NOPAGETHEME;
 
+    // Give it some reasonably big minimal size by default.
     m_book = new WidgetsBookCtrl(m_panel, Widgets_BookCtrl,
-                                 wxDefaultPosition, wxDefaultSize,
+                                 wxDefaultPosition, FromDIP(wxSize(900, 500)),
                                  style, "Widgets");
 
     InitBook();