Improve wxRadioBox height on wxMSW

With larger fonts, there is an excessive gap between the box and the first (and last) radio button.
Instead of using the dynamic character size, use the fixed size of the radio button to determine this height.

src/msw/radiobox.cpp

@@ -582,7 +582,8 @@ wxSize wxRadioBox::GetTotalButtonSize(const wxSize& sizeBtn) const
 
     // Add extra space under the label, if it exists.
     if (!wxControl::GetLabel().empty())
-        height += cy1/2;
+        height += wxRendererNative::Get().GetCheckBoxSize(
+            reinterpret_cast<wxWindow*>(const_cast<wxRadioBox*>(this))).y / 2;
 
     // and also wide enough for its label
     int widthLabel;
@@ -658,7 +659,8 @@ wxRadioBox::PositionAllButtons(int x, int y, int width, int WXUNUSED(height))
 
     // Add extra space under the label, if it exists.
     if (!wxControl::GetLabel().empty())
-        y_offset += cy1/2;
+        y_offset += wxRendererNative::Get().GetCheckBoxSize(
+            reinterpret_cast<wxWindow*>(this)).y / 2;
 
     int startX = x_offset;
     int startY = y_offset;