Updated the changelog

CHANGELOG.md

@@ -1,24 +1,20 @@
 ## vNext (TBD)
 
+### Notes
+Based on Realm JS v10.21.0: See changelog below for details on enhancements and fixes introduced between this and the previous pre release (which was based on Realm JS v10.19.5).
+
 ### Enhancements
 * Small improvement to performance by caching JSI property String object [#4863](https://github.com/realm/realm-js/pull/4863)
 
 ### Fixed
-* <How to hit and notice issue? what was the impact?> ([#????](https://github.com/realm/realm-js/issues/????), since v?.?.?)
 * None.
 
 ### Compatibility
-* React Native >= v0.64.0
+* React Native >= v0.70.0
 * Atlas App Services.
 * Realm Studio v12.0.0.
-* APIs are backwards compatible with all previous releases of Realm JavaScript in the 10.5.x series.
 * File format: generates Realms with format v22 (reads and upgrades file format v5 or later for non-synced Realm, upgrades file format v10 or later for synced Realms).
 
-### Internal
-<!-- * Either mention core version or upgrade -->
-<!-- * Using Realm Core vX.Y.Z -->
-<!-- * Upgraded Realm Core from vX.Y.Z to vA.B.C -->
-
 ## 10.21.0 (2022-09-09)
 
 ### Enhancements