[animations] Clarify that onClosed is called before transition (#10400)

Updated the documentation for `OpenContainer.onClosed` to clarify that it is called at the start of the closing transition, not at the end.

Resolves flutter/flutter#178314

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[^1]: This PR only affects comments/documentation.

Author: adil192

packages/animations/CHANGELOG.md

@@ -1,5 +1,6 @@
-## NEXT
+## 2.1.1
 
+* Updated the documentation for `OpenContainer.onClosed` to clarify that it is called at the start of the closing transition, not at the end.
 * Updates minimum supported SDK version to Flutter 3.32/Dart 3.8.
 
 ## 2.1.0

packages/animations/lib/src/open_container.dart

@@ -190,7 +190,8 @@ class OpenContainer<T extends Object?> extends StatefulWidget {
   ///  * [Material.shape], which is used to implement this property.
   final ShapeBorder openShape;
 
-  /// Called when the container was popped and has returned to the closed state.
+  /// Called when the container is popped. This is called at the start of the
+  /// closing transition.
   ///
   /// The return value from the popped screen is passed to this function as an
   /// argument.

packages/animations/pubspec.yaml

@@ -2,7 +2,7 @@ name: animations
 description: Fancy pre-built animations that can easily be integrated into any Flutter application.
 repository: https://github.com/flutter/packages/tree/main/packages/animations
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+animations%22
-version: 2.1.0
+version: 2.1.1
 
 environment:
   sdk: ^3.8.0