Remove unnecessary dynamic cast to wxPseudoTransparentFrame

Just test whether we're using "Venetian blinds" hint directly instead of
testing for whether we use wxPseudoTransparentFrame which can be also
used for the default transparent hint if transparency is not supported
natively.

This doesn't change much in practice, but just avoid using dynamic cast
unnecessarily.

src/aui/framemanager.cpp

@@ -3314,7 +3314,7 @@ void wxAuiManager::ShowHint(const wxRect& rect)
         m_hintFadeAmt = m_hintFadeMax;
 
         if ((m_flags & wxAUI_MGR_HINT_FADE)
-            && !((wxDynamicCast(m_hintWnd, wxPseudoTransparentFrame)) &&
+            && !((m_flags & wxAUI_MGR_VENETIAN_BLINDS_HINT) &&
                  (m_flags & wxAUI_MGR_NO_VENETIAN_BLINDS_FADE))
             )
             m_hintFadeAmt = 0;