Update Crashlytics/CHANGELOG.md

Co-authored-by: Nick Cooke <36927374+ncooke3@users.noreply.github.com>

Author: mghaznav

Crashlytics/CHANGELOG.md

@@ -2,8 +2,14 @@
 - [fixed] Fixed a deadlock in Firebase Sessions where the main thread could
   block waiting for a lock held by a background thread during settings
   updates. (#15394)
+# Unreleased
 - [fixed] Fixed an issue where Crashlytics API calls were silently dropped if invoked immediately after Firebase initialization.
 
+# 12.10.0
+- [fixed] Fixed a deadlock in Firebase Sessions where the main thread could
+block waiting for a lock held by a background thread during settings
+updates. (#15394)
+
 # 12.9.0
 - [fixed] Conformed to Mach IPC security restrictions. (#15393)