Remove workaround for ROOT/cling problem with Boost small_vector

To be used for creating a reproducer and testing upcoming ROOT builds.

closes #75

Kernel/LHCbKernel/include/Kernel/DD4HEP/RichTypes.h

@@ -95,11 +95,11 @@ namespace Rich {
   using RadiatorArray = std::array<TYPE, NRadiatorTypes>;
 
   /// Type for container of detector types
-  using Detectors = boost::container::small_vector<DetectorType, N_DETECTOR_TYPES, void, void>;
+  using Detectors = boost::container::small_vector<DetectorType, N_DETECTOR_TYPES>;
   /// Type for container of side types
-  using Sides = boost::container::small_vector<Side, N_SIDE_TYPES, void, void>;
+  using Sides = boost::container::small_vector<Side, N_SIDE_TYPES>;
   /// Type for container of radiator types
-  using Radiators = boost::container::small_vector<RadiatorType, N_RADIATOR_TYPES, void, void>;
+  using Radiators = boost::container::small_vector<RadiatorType, N_RADIATOR_TYPES>;
 
   /// Access all valid detector types
   inline Detectors detectors() noexcept { return {Rich::Rich1, Rich::Rich2}; }

Kernel/LHCbKernel/include/Kernel/MonotonicArena.h

@@ -65,10 +65,8 @@ namespace LHCb::Arena {
     /// One byte past the end of the current block, or nullptr if it doesn't exist.
     std::byte* m_current_end{nullptr};
 
-    // Explicitly specify boost::container::small_vector default template arguments
-    // to sidestep cling error, see lhcb/LHCb#75
     /// All memory blocks owned by this arena.
-    boost::container::small_vector<gsl::span<std::byte>, 1, void, void> m_all_blocks;
+    boost::container::small_vector<gsl::span<std::byte>, 1> m_all_blocks;
 
     /// Approximate factor by which each block is larger than its predecessor.
     static constexpr std::size_t growth_factor = 2;

Kernel/LHCbKernel/include/Kernel/RichParticleIDType.h

@@ -69,10 +69,8 @@ namespace Rich {
   template <typename TYPE>
   using ParticleArray = std::array<TYPE, NParticleTypes>;
 
-  // Explicitly specify boost::container::small_vector default template arguments
-  // to sidestep cling error, see lhcb/LHCb#75
   /// Type for container of particle types
-  using Particles = boost::container::small_vector<ParticleIDType, N_PARTICLE_TYPES, void, void>;
+  using Particles = boost::container::small_vector<ParticleIDType, N_PARTICLE_TYPES>;
 
   /// Access all valid particle ID types
   inline Particles particles() noexcept {

Kernel/LHCbKernel/include/Kernel/RichRadIntersection.h

@@ -53,10 +53,8 @@ namespace Rich {
   class RadIntersection {
 
   public:
-    // Explicitly specify boost::container::small_vector default template arguments
-    // to sidestep cling error, see lhcb/LHCb#75
     /// Definition of a vector of intersections
-    using Vector = boost::container::small_vector<Rich::RadIntersection, 1, void, void>;
+    using Vector = boost::container::small_vector<Rich::RadIntersection, 1>;
 
   public:
     /// Default constructor