Update CHANGELOG for Firestore v1.9.0 (#4626)

wilhuff · web-flow · commit fe822f4fab33 · 2020-01-08T09:14:15.000-08:00
diff --git a/Firestore/CHANGELOG.md b/Firestore/CHANGELOG.md
@@ -1,4 +1,6 @@
 # Unreleased
+
+# v1.9.0
 - [feature] Added a `limit(toLast:)` query operator, which returns the last
   matching documents up to the given limit.
 
