Update CHANGELOG for #8459

CHANGELOG.md

@@ -1,12 +1,18 @@
 ## 2.11.0 (Unreleased)
 
+NOTES:
+
+* resource/aws_emr_cluster: The `instance_group` configuration block, `master_instance_type` argument, `core_instance_count` argument, and `core_instance_type` argument have been deprecated in favor of new `master_instance_group` and `core_instance_group` configuration blocks. The older, conflicting configurations were problematic in update scenarios. Task instance groups can be managed with the `aws_emr_instance_group` resource. Upgrade instructions can be found in the new Version 3 Upgrade Guide. [GH-8459]
+
 FEATURES:
 
 * **New Data Source:** `aws_ecr_image` [GH-8403]
+* **New Guide:** Version 3 Upgrade Guide [GH-8459]
 
 ENHANCEMENTS:
 
 * resource/aws_autoscaling_schedule: Support resource import [GH-8300]
+* resource/aws_emr_cluster: Add `master_instance_group` and `core_instance_group` configuration blocks (deprecates other instance group configuration methods) [GH-8459]
 
 BUG FIXES: