align naming

Author: gareth-johnston

protocol-definitions/custom/Custom.yaml

@@ -989,7 +989,7 @@ customTypes:
         type: Address
         nullable: false
         since: 2.1
-      - name: autoStepsDownWhenLeader
+      - name: autoStepDownWhenLeader
         type: boolean
         nullable: false
         since: 2.9