Remove Whole Tag from document_mappings generation

This is ignored by the Redirector so does not need to be produced.
Removing obsolete script

It looks like this is superceded by dump_all_admin_to_public_documents_and_non_documents.rb. Removing it rather than making Whole Tag changes as I do not think it is required.
Merge pull request #267 from alphagov/remove-whole-tag

Remove Whole Tag