Remove the "ifndef __WRAP__" from vtkAtomicInt.h.

On Oct 9, the wrappers were fixed so that they can parse the code
that was blocked off by "#ifndef __WRAP__" in vtkAtomicInt.h.in.

Change-Id: I1ef1ab4e7709b22ca5a59108a8cff9bb47c42a70
Merge topic 'remove-ifndef-wrap' into master

64498221 Remove the "ifndef __WRAP__" from vtkAtomicInt.h.