Remove unnecessary wxSizer::Fit() calls

wxSizer::SetSizeHints() already does what Fit() does (while also setting
the minimum window size to the fitting size), so there is no need to
call both of them.

No real changes, just some cleanup.

src/generic/msgdlgg.cpp

@@ -220,7 +220,6 @@ void wxGenericMessageDialog::DoCreateMsgdialog()
     SetSizer( topsizer );
 
     topsizer->SetSizeHints( this );
-    topsizer->Fit( this );
     wxSize size( GetSize() );
     if (size.x < size.y*3/2)
     {