DOCS-15686 Fixing Change Event Syntax error (#2360)

* DOCS-15686 Fixing Change Event Syntax error

* space

Author: ianf-mongodb

source/reference/change-events.txt

@@ -160,11 +160,12 @@ For example:
 
 .. code-block:: javascript
 
-   let cur = db.names.aggregate( [
-      $changeStream: {
-         showExpandedEvents: true
+   let cur = db.names.aggregate( [ { 
+      $changeStream: { 
+          showExpandedEvents: true 
+        } 
       }
-   ] )
+    ] )
 
    cur.next()