MCRecoTrackerHitPlaneAssociation can / should be removed

[tmadlener]

Currently we have two associations for SimTrackerHit to reco level tracker hits:

EDM4hep/edm4hep.yaml

Lines 633 to 649 in a296139

	edm4hep::MCRecoTrackerAssociation:
	Description: "Association between a TrackerHit and the corresponding SimTrackerHit"
	Author: "EDM4hep authors"
	Members:
	- float weight // weight of this association
	OneToOneRelations:
	- edm4hep::TrackerHit rec // reference to the reconstructed hit
	- edm4hep::SimTrackerHit sim // reference to the simulated hit
	edm4hep::MCRecoTrackerHitPlaneAssociation:
	Description: "Association between a TrackerHitPlane and the corresponding SimTrackerHit"
	Author: "EDM4hep authors"
	Members:
	- float weight // weight of this association
	OneToOneRelations:
	- edm4hep::TrackerHitPlane rec // reference to the reconstructed hit
	- edm4hep::SimTrackerHit sim // reference to the simulated hit

I am fairly certain these are leftovers from before the introduction of the TrackerHit interface (#252) and the dedicated MCRecoTrackerHitPlaneAssociation has become obsolete by now. I am not entirely sure whether we can simply drop it transparently.

In any case this should also go in before v1.0.