Update autorest.md (Azure#49189)

Author: HarveyLink

sdk/resourcemanager/Azure.ResourceManager/src/autorest.md

@@ -13,7 +13,6 @@ head-as-boolean: false
 modelerfour:
   lenient-model-deduplication: true
 use-model-reader-writer: true
-use-write-core: true
 deserialize-null-collection-as-null-value: true
 enable-bicep-serialization: true