Remove deprecated ``NPY_ARRAY_UPDATEIFCOPY``
--------------------------------------------

The array flag ``UPDATEIFCOPY`` and enum ``NPY_ARRAY_UPDATEIFCOPY`` were
deprecated in 1.14. They were replaced by ``WRITEBACKIFCOPY`` which require
calling ``PyArray_ResoveWritebackIfCopy`` before the array is deallocated. Also
removed the associated (and deprecated) ``PyArray_XDECREF_ERR``.
