Fix TimeHistogramPerTimeline to count chunks not components

The histogram was incorrectly incrementing/decrementing by event.num_components()
instead of 1. This caused timelines with 'wide' archetypes (many components) to
appear far more active than timelines with few components, breaking timeline
selection and navigation logic.

Author: joelreymont

crates/store/re_entity_db/src/time_histogram_per_timeline.rs

@@ -149,10 +149,10 @@ impl ChunkStoreSubscriber for TimeHistogramPerTimeline {
                 .collect_vec();
             match event.kind {
                 ChunkStoreDiffKind::Addition => {
-                    self.add(&times, event.num_components() as _);
+                    self.add(&times, 1);
                 }
                 ChunkStoreDiffKind::Deletion => {
-                    self.remove(&times, event.num_components() as _);
+                    self.remove(&times, 1);
                 }
             }
         }