edm4eic.yaml: fix MCRecoTrackerHitAssociation to relate to a single sim hit at a time (#77)

I believe, having sim hits as a OneToMany relation was a mistake. The
idea behind having a weight is to specify level of contribution of a
specific sim hit. If multiple sim hits are associated, user should
expect multiple association records in the collection. We are only now
introducing the actual use of this, so now is the good time to do a fix
eic/EICrecon#1392 (comment)

cc @wdconinc @c-dilks

Author: veprbl

CMakeLists.txt

@@ -6,7 +6,7 @@ cmake_minimum_required(VERSION 3.12)
 project(EDM4EIC
   LANGUAGES CXX)
 
-SET( ${PROJECT_NAME}_VERSION_MAJOR 5 )
+SET( ${PROJECT_NAME}_VERSION_MAJOR 6 )
 SET( ${PROJECT_NAME}_VERSION_MINOR 0 )
 SET( ${PROJECT_NAME}_VERSION_PATCH 0 )
 SET( ${PROJECT_NAME}_VERSION  "${${PROJECT_NAME}_VERSION_MAJOR}.${${PROJECT_NAME}_VERSION_MINOR}.${${PROJECT_NAME}_VERSION_PATCH}" )

edm4eic.yaml

@@ -546,5 +546,4 @@ datatypes:
       - float                 weight        // weight of this association
     OneToOneRelations:
      - edm4eic::RawTrackerHit rawHit        // reference to the digitized hit
-    OneToManyRelations:
-     - edm4hep::SimTrackerHit simHits       // reference to the simulated hits
+     - edm4hep::SimTrackerHit simHit       // reference to the simulated hit