Don't expand wxChoice-based grid editor vertically

This just looks very strange if the row has much bigger height than
default and it already isn't done for other editors, e.g. those using
wxSpinCtrl or wxDatePickerCtrl, for the same reason, so this is also
more consistent.

src/generic/grideditors.cpp

@@ -1447,12 +1447,16 @@ void wxGridCellChoiceEditor::SetSize(const wxRect& rect)
     wxASSERT_MSG(m_control,
                  wxT("The wxGridCellChoiceEditor must be created first!"));
 
-    // Check that the rectangle is big enough to fit the combobox, we can't
-    // afford truncating it.
-    wxSize size = rect.GetSize();
-    size.IncTo(m_control->GetBestSize());
+    // Use normal wxChoice size, except for extending it to fill the cell
+    // width: we can't be smaller because this could make the control unusable
+    // and we don't want to be taller because this looks unusual and weird.
+    wxSize size = m_control->GetBestSize();
+    if ( size.x < rect.width )
+        size.x = rect.width;
 
-    wxGridCellEditor::SetSize(wxRect(size).CentreIn(rect));
+    wxRect rectChoice(rect.GetPosition(), size);
+
+    wxGridCellEditor::SetSize(rectChoice.CenterIn(rect, wxVERTICAL));
 }
 
 void wxGridCellChoiceEditor::PaintBackground(wxDC& dc,