reword (#730)

(cherry picked from commit 5344333)

Author: mongoKart

source/whats-new.txt

@@ -124,7 +124,7 @@ New features of the 5.4 {+driver-short+} release include:
 
 .. important:: Deprecation Notice
 
-  - The ``collStats`` helper command is deprecated. Use the :manual:`$collStats
+  - The ``collStats`` operation is deprecated. Use the :manual:`$collStats
     </reference/operator/aggregation/collStats>` aggregation operator instead.
   - The TypeScript interface passed to the ``db.command()`` method incorrectly
     includes certain options. These options have been deprecated.