Remove deprecated functions

[tmadlener]

BEGINRELEASENOTES

• Remove deprecated conversion functions now that all downstream consumers have switched.
• Remove association (and derived terms) from documentation, variable names and comments.

ENDRELEASENOTES

These were introduced in #86 and #54 to decouple the changes from necessary fixes in k4MarlinWrapper.

• [x] Needs https://github.com/key4hep/k4MarlinWrapper/pull/200

[jmcarcell]

Somehow related to the change from Association to Link, Association is still used in several places in tests:

tests/src/CompareEDM4hepLCIO.h
235:bool compareVertexRecoAssociation(const EVENT::Vertex* lcioVtx, const edm4hep::VertexRecoParticleLink& association,

tests/src/CompareEDM4hepLCIO.cc
477:// bool compareStartVertexRelations(const edm4hep::VertexRecoParticleLinkCollection& startVtxAssociations, const
479://   for (const auto& assoc : startVtxAssociations) {
497:bool compareVertexRecoAssociation(const EVENT::Vertex*, const edm4hep::VertexRecoParticleLink&, const ObjectMappings&) {

tests/src/EDM4hep2LCIOUtilities.cc
352:AssocCollT createAssociationCollection(const CollT& collA, const CollU& collB) {
370:  return createAssociationCollection<edm4hep::RecoMCParticleLinkCollection>(mcParticles, recoParticles);
376:  return createAssociationCollection<edm4hep::CaloHitSimCaloHitLinkCollection>(simHits, caloHits);

tests/src/CompareEDM4hepEDM4hep.h
44:template <typename AssociationCollT>
45:bool compare(const AssociationCollT& origColl, const AssociationCollT& roundtripColl) {

tests/src/CompareEDM4hepLCIO.h
235:bool compareVertexRecoAssociation(const EVENT::Vertex* lcioVtx, const edm4hep::VertexRecoParticleLink& association,

And then in some other places related to documentation:

k4EDM4hep2LcioConv/src/k4Lcio2EDM4hepConv.cpp
89:      // We handle Relations (aka Associations) once we have converted all the
115:  // AssociationCollections.

k4EDM4hep2LcioConv/include/k4EDM4hep2LcioConv/k4EDM4hep2LcioConv.h
440: * Create an LCRelation collection from the passed Association Collection

doc/LCIO2EDM4hep.md
131:The AssociationCollections in EDM4hep are then created using `createAssociations`.

[tmadlener]

There were also quite a few assoc and other similar thing. I think I got most of them.