Do not set focus to the window when its rich tooltip is shown

Don't set the focus to the window the rich tooltip refers to in its
ShowFor() method because this was inconsistent with plain tooltips and
also could result in infinite recursion if the window decided to show
its tooltip when it got focus.

Closes https://github.com/wxWidgets/wxWidgets/pull/1265

src/generic/richtooltipg.cpp

@@ -667,9 +667,6 @@ void wxRichToolTipGenericImpl::SetTitleFont(const wxFont& font)
 
 void wxRichToolTipGenericImpl::ShowFor(wxWindow* win, const wxRect* rect)
 {
-    // Set the focus to the window the tooltip refers to to make it look active.
-    win->SetFocus();
-
     wxRichToolTipPopup* const popup = new wxRichToolTipPopup
                                           (
                                             win,