remove duplicate override, correct FieldMap
remove duplicate override, correct FieldMap

mkb137/FSharp.TypeProviders.StarterPack,fsprojects/FSharp.TypeProviders.SDK,fsprojects/FSharp.TypeProviders.StarterPack,mavnn/FSharp.TypeProviders.StarterPack,rflechner/FSharp.TypeProviders.StarterPack,tpetricek/FSharp.TypeProviders.StarterPack,dsyme/FSharp.TypeProviders.StarterPack,cloudRoutine/FSharp.TypeProviders.StarterPack,sergey-tihon/FSharp.TypeProviders.StarterPack,delegateas/FSharp.TypeProviders.StarterPack