BUG: Memory leak. Reported by Coverity.

It was missing to call delete on an allocated array.

It was reported by Coverity as:

    1081112 Resource leak

    The system resource will not be reclaimed and reused, reducing the future
    availability of the resource.

    In itk::​MeshIOBase::​WriteBufferAsBinary<…>(T2 *,
     std::​basic_ofstream<char, std::​char_traits<char>> &, unsigned long):
     Leak of memory or pointers to system resources.

Change-Id: I0822f7332a203a7cdd89b72de2365c67189feabc
Merge topic 'coverity_cid_1081112_resource_leak_p2'

8456bb9 BUG: Memory leak. Reported by Coverity.