DIM2DataCite.xsl: update XML namespace to DataCite kernel version 4

[saschaszott]

Description

DIM2DataCite.xsl uses schema elements, e.g. givenName and familyName, that were added in DataCite kernel version 4 (https://schema.datacite.org/meta/kernel-4/metadata.xsd).

Currently, the XSL stylesheet DIM2DataCite.xsl refers to kernel version 3 (https://schema.datacite.org/meta/kernel-3/metadata.xsd) that does not contain givenName and familyName.

[saschaszott]

@abollini this PR should be back-ported to DSC7 (branch https://github.com/4Science/DSpace/tree/dspace-cris-2023_02_x) as well.

[abollini]

hi @saschaszott
thanks for proposing that. DSpace-CRIS is now using its internal export framework to generate datacite metadata both for DOI minting that just export of an item in the datacite metadata format. This change is not longer needed. We should remove the xsl completely but we are just leaving it unmaintained for who are still using it