Use ClassDefOverride in the derived interaction samplers

This fixes the -Winconsistent-missing-override warnings in InteractionSampler.h.

- FixedSkipBC_InteractionSampler and NonUniformMuInteractionSampler derive from InteractionSampler, which already has a ClassDef.
- Their plain ClassDef produced override warnings for IsA, ShowMembers, Streamer and CheckTObjectHashConsistency.
- Both now use ClassDefOverride.

https://ali-ci.cern.ch/alice-build-logs/AliceO2Group/AliceO2/15843/ee5503a4c432ac109fab4860dde02f104c65e5a6/build_O2_gpu-test-slc10-x86/pretty.html

Author: sawenzel

DataFormats/simulation/include/SimulationDataFormat/InteractionSampler.h

@@ -128,7 +128,7 @@ class FixedSkipBC_InteractionSampler : public InteractionSampler
  private:
   int mEveryN;       // the skip number ---> fills every N-th BC in the bunch filling scheme
   int mMultiplicity; // how many events to put if bc is filled
-  ClassDef(FixedSkipBC_InteractionSampler, 1);
+  ClassDefOverride(FixedSkipBC_InteractionSampler, 1);
 };
 
 // A version of the interaction sampler which can sample according to non-uniform mu(bc) as
@@ -152,7 +152,7 @@ class NonUniformMuInteractionSampler : public InteractionSampler
  private:
   // non-uniformity
   std::vector<float> mBCIntensityScales;
-  ClassDef(NonUniformMuInteractionSampler, 1);
+  ClassDefOverride(NonUniformMuInteractionSampler, 1);
 };
 
 } // namespace steer