remove suffix Module on namespace for better C# interop (#19)

Namespace was `MongoDB.Bson.Serialization.FSharp` for F# and
`MongoDB.Bson.Serialization.FSharpModule` for C#.
Unify this under `MongoDB.Bson.Serialization.FSharp`.

Author: pchalamet

src/FSharp.MongoDB.Bson/Serialization/FSharpValueSerializer.fs

@@ -20,7 +20,6 @@ open MongoDB.Bson.Serialization.Conventions
 open MongoDB.Bson.Serialization.Helpers
 open MongoDB.Bson.Serialization.Serializers
 
-[<CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
 [<RequireQualifiedAccess>]
 module FSharp =