Merge branch 'Claire_fixyfix' into 'master'

Make PVtracks::containers() access method const

See merge request !3709

Event/RecEvent/include/Event/PrimaryVertices.h

@@ -62,7 +62,7 @@ namespace LHCb::Event::PV {
 
     // Required to get to the velo tracks
     template <typename Tag>
-    auto containers() {
+    auto containers() const {
       if constexpr ( std::is_same_v<Tag, PVTrackTag::veloindex> ) { return prvelocontainers; }
     }
     std::array<const PrVeloTracks*, 2> prvelocontainers; // forward, backward