KAFKA-20290: KIP-1240 updates in upgrade.md (apache#21703)

Add a line to upgrade.md for KIP-1240.

Reviewers: Lan Ding <isDing_L@163.com>, majialong
 <majialoong@gmail.com>, Lianet Magrans <lmagrans@confluent.io>

Author: AndrewJSchofield

docs/getting-started/upgrade.md

@@ -39,6 +39,7 @@ type: docs
   * The `kafka-streams-scala` library is deprecated as of Kafka 4.3 and will be removed in Kafka 5.0. For further details, please refer to the [migration guide](/{version}/streams/developer-guide/scala-migration).
   * Support for cordoning log directories: For further details, please refer to [KIP-1066](https://cwiki.apache.org/confluence/x/Lg_TEg).
   * The `group.coordinator.rebalance.protocols` configuration is deprecated and will be removed in Kafka 5.0. In Kafka 5.0, all protocols will always be enabled and controlled solely by feature versions (`group.version`, `streams.version`, `share.version`) via `kafka-features.sh`. For further details, please refer to [KIP-1237](https://cwiki.apache.org/confluence/x/jIqmFw).
+  * New group configs have been introduced: `share.delivery.count.limit`, `share.partition.max.record.locks` and `share.renew.acknowledge.enable`, along with equivalent broker configs for specifying minimum and maximum values. In addition, the validation of group configs has been improved. For further details, please refer to [KIP-1240](https://cwiki.apache.org/confluence/x/tIHMFw).
 
 ## Upgrading to 4.2.0