Fix namespace Fable.React => Fable.Helpers.React

Author: 0x53A

docs/using-third-party-react-components.md

@@ -72,7 +72,7 @@ In the example of rc-progress, to declare a `progressLine` creation function tha
 
 ```fsharp
 open Fable.Core
-open Fable.React
+open Fable.Helpers.React
 open Fable.Import.React
 open Fable.Core.JsInterop