reinstate RDF::Repository::Implementation::SerializedTransaction
reinstate RDF::Repository::Implementation::SerializedTransaction

readds compatiblity for public name
RDF::Repository::Implementation::SerializedTransaction.

with the release of 3.2.0/3.2.1, downstream applications see failing builds due
to the removal of this name. at first glance, it appears that readding the name
reinstates compatibility.

ruby-rdf/rdf