[FIX] sap.ui.rta - fix missing lrep serializer for saveAs appVariant
[FIX] sap.ui.rta - fix missing lrep serializer for saveAs appVariant

BCP: 2270123762
Change-Id: I228d9ad1fad1ec002114a6e9a845c1b6e6aaa86d

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