Set up target date for release

Signed-off-by: Friedrich Gonzalez <1517449+friedrichg@users.noreply.github.com>

Author: friedrichg

CHANGELOG.md

@@ -1,6 +1,6 @@
 # Changelog
 
-## 1.21.1 / unreleased
+## 1.21.1 / 2026-06-01
 
 * [BUGFIX] gRPC: Fix panic when `grpc_compression` is set to `snappy` on ingester client or store-gateway client configurations. #7459
 * [BUGFIX] Config: Mask Swift, etcd, Redis, and HTTP basic-auth credentials on the `/config` endpoint. #7473