update sync to 1.9.2 & core to 2.8.1
update sync to 1.9.2 & core to 2.8.1

realm/realm-object-store,realm/realm-object-store,realm/realm-object-store,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core