Update CHANGELOG.md (#12170)

Author: ehsannas

Firestore/CHANGELOG.md

@@ -1,8 +1,6 @@
 # 10.19.0
-- [fixed] Fixed an issue in the local cache synchronization logic where all
-  locally-cached documents that matched a resumed query would be unnecessarily
-  re-downloaded; with the fix it now only downloads the documents that are known
-  to be out-of-sync. (#12044)
+- [fixed] Made an optimization to the synchronization logic for resumed queries
+  to only re-download locally-cached documents that are known to be out-of-sync. (#12044)
 
 # 10.18.0
 - [fixed] Fix Firestore build for visionOS on Xcode 15.1. (#12023)