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.

Fixes the bug introduced in dd55e00.

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);
                 }
             }
         }