Remove duplicate definition of xpmem_apid_t

cmr=v1.7.5:ticket=trac:4216

This commit was SVN r30589.

The following Trac tickets were found above:
  Ticket 4216 --> https://svn.open-mpi.org/trac/ompi/ticket/4216

ompi/mca/btl/vader/btl_vader.h

@@ -51,7 +51,6 @@
     #include <sn/xpmem.h>
 
     typedef int64_t xpmem_segid_t;
-    typedef int64_t xpmem_apid_t;
   #endif
 #else
 #include "opal/mca/shmem/base/base.h"