Update changelog based on model updates

Author: aws-sdk-python-automation

.changes/next-release/api-change-medialive-44580.json

@@ -0,0 +1,5 @@
+{
+  "type": "api-change",
+  "category": "``medialive``",
+  "description": "AWS Elemental MediaLive now supports Pipeline Locking using Video Alignment as well as linked single pipeline channels to enable cross-channel and cross-region Pipeline Locking workflows."
+}