Mark release 1.21.0 in progress (#7341)

Signed-off-by: Friedrich Gonzalez <[email protected]>

Author: friedrichg

CHANGELOG.md

@@ -1,6 +1,9 @@
 # Changelog
 
 ## master / unreleased
+
+## 1.21.0 in progress
+
 * [CHANGE] Ruler: Graduate Ruler API from experimental. #7312
   * Flag: Renamed `-experimental.ruler.enable-api` to `-ruler.enable-api`. The old flag is kept as deprecated.
   * Ruler API is no longer marked as experimental.
@@ -22,7 +25,7 @@
 * [FEATURE] Distributor: Add a per-tenant flag `-distributor.enable-type-and-unit-labels` that enables adding `__unit__` and `__type__` labels for remote write v2 and OTLP requests. This is a breaking change; the `-distributor.otlp.enable-type-and-unit-labels` flag is now deprecated, operates as a no-op, and has been consolidated into this new flag. #7077
 * [FEATURE] Querier: Add experimental projection pushdown support in Parquet Queryable. #7152
 * [FEATURE] Ingester: Add experimental active series queried metric. #7173
-* [FEATURE] Update prometheus Alertmanager version to v0.31.1 and add new integration to mattermost. #7267
+* [FEATURE] Update prometheus Alertmanager version to v0.31.1 and add new integration to IncidentIO and Mattermost. #7092 #7267
 * [ENHANCEMENT] Distributor: Add `cortex_distributor_push_requests_total` metric to track the number of push requests by type. #7239
 * [ENHANCEMENT] Querier: Add `-querier.store-gateway-series-batch-size` flag to configure the maximum number of series to be batched in a single gRPC response message from Store Gateways. #7203
 * [ENHANCEMENT] HATracker: Add `-distributor.ha-tracker.enable-startup-sync` flag. If enabled, the ha-tracker fetches all tracked keys on startup to populate the local cache. #7213
@@ -32,7 +35,6 @@
 * [ENHANCEMENT] Distributor: Skip attaching `__unit__` and `__type__` labels when `-distributor.enable-type-and-unit-labels` is enabled, as these are appended from metadata. #7145
 * [ENHANCEMENT] Distributor: Add `cortex_distributor_ingester_push_timeouts_total` metric to track the number of push requests to ingesters that were canceled due to timeout. #7155 #7229
 * [ENHANCEMENT] StoreGateway: Add tracings to parquet mode. #7125
-* [ENHANCEMENT] Alertmanager: Upgrade alertmanger to 0.29.0 and add a new incidentIO integration. #7092
 * [ENHANCEMENT] Querier: Add a `-querier.parquet-queryable-shard-cache-ttl` flag to add TTL to parquet shard cache. #7098
 * [ENHANCEMENT] Ingester: Add `enable_matcher_optimization` config to apply low selectivity matchers lazily. #7063
 * [ENHANCEMENT] Distributor: Add a label references validation for remote write v2 request. #7074
@@ -43,7 +45,7 @@
 * [ENHANCEMENT] Compactor: Avoid double compaction by cleaning partition files in 2 cycles. #7130 #7209 #7257
 * [ENHANCEMENT] Distributor: Optimize memory usage by recycling v2 requests. #7131
 * [ENHANCEMENT] Compactor: Avoid double compaction by not filtering delete blocks on real time when using bucketIndex lister. #7156
-* [ENHANCEMENT] Upgrade to go 1.25. #7164 #7340
+* [ENHANCEMENT] Upgrade to go 1.25.8 #7164 #7340
 * [ENHANCEMENT] Upgraded container base images to `alpine:3.23`. #7163
 * [ENHANCEMENT] Ingester: Instrument Ingester CPU profile with userID for read APIs. #7184
 * [ENHANCEMENT] Ingester: Add fetch timeout for Ingester expanded postings cache. #7185