Add changelog for list validation optimization. (boto#3626)

Author: SamRemis

.changes/next-release/enhancement-Validation-77540.json

@@ -0,0 +1,5 @@
+{
+  "type": "enhancement",
+  "category": "Validation",
+  "description": "Updated list validation to add fast-path for list members that only require basic type checking."
+}