logtree: chase out some documentation typos

Test Plan: only documentation changes.

X-Origin-Diff: phab/D627
GitOrigin-RevId: 78b1983bd67c632f467227689371113f26da5842
diff --git a/core/pkg/logtree/doc.go b/core/pkg/logtree/doc.go
index 5445e2e..caef97a 100644
--- a/core/pkg/logtree/doc.go
+++ b/core/pkg/logtree/doc.go
@@ -28,13 +28,13 @@
 
 Tree Structure
 
-As an example, consider application that produces logs with the following DNs:
+As an example, consider an application that produces logs with the following DNs:
 
     listener.http
-	listener.grpc
-	svc
-	svc.cache
-	svc.cache.gc
+    listener.grpc
+    svc
+    svc.cache
+    svc.cache.gc
 
 This would correspond to a tree as follows: