Remove the inclusions of wx/cocoa headers which don't exist any more.

This should have been part of r76735: in addition to removing the old Cocoa
port headers, also remove the references to them from the common include
files.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76806 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/colour.h

@@ -219,8 +219,6 @@ WXDLLIMPEXP_CORE bool wxFromString(const wxString& str, wxColourBase* col);
     #include "wx/x11/colour.h"
 #elif defined(__WXMAC__)
     #include "wx/osx/colour.h"
-#elif defined(__WXCOCOA__)
-    #include "wx/cocoa/colour.h"
 #endif
 
 #define wxColor wxColour