Improve change summary

Author: nicktindall

docs/changelog/126581.yaml

@@ -1,5 +1,10 @@
 pr: 126581
-summary: Evict from the shared blob cache asynchronously
+summary: "Optimize shared blob cache evictions on shard removal
+  Shared blob cache evictions occur on the cluster applier thread when shards are
+  removed from a node. These can be expensive if a large number of shards are
+  being removed. This change uses the context of the removal to avoid unnecessary
+  evictions that might hold up the applier thread.
+  "
 area: Snapshot/Restore
 type: enhancement
 issues: []