[INTERNAL] sap.ui.model.Model: enhance JsDoc for propertyChange event
[INTERNAL] sap.ui.model.Model: enhance JsDoc for propertyChange event

PS1: Done

Change-Id: Ib0f24cd368e36d8a9db3677538d4815ac8e1f2ca
demo-kit-feedback: 4478

SAP/openui5,SAP/openui5,SAP/openui5,SAP/openui5