remove unboxed doc, point it to untagged variant

misc_docs/syntax/decorator_unboxed.mdx

@@ -7,15 +7,16 @@ category: "decorators"
 ---
 
 The `@unboxed` decorator provides a way to unwrap **variant** constructors
-that have a *single* argument, or **record** objects that have a *single* field.
+that have no overlap in their runtime representation, or **record** objects that have a *single* field.
 
 ### Example
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
 ```res
 @unboxed
-type name = Name(string)
+type listItemValue = String(string) | Boolean(bool) | Number(float)
+let myArray = [String("Hello"), Boolean(true), Boolean(false), Number(13.37)]
 let studentName = Name("Joe")
 
 @unboxed
@@ -24,12 +25,16 @@ let hi = {message: "hello!"}
 ```
 
 ```js
-var studentName = "Joe";
+var myArray = ["hello", true, false, 13.37];
 var hi = "hello!";
 ```
 
 </CodeTab>
 
+_`@unboxed` for variants with multiple constructors is available since ReScript `11.0.0`._
+
 ### References
 
-* [Unboxed](/docs/manual/latest/unboxed)
+* [Untagged variants doc](/docs/manual/latest/variant#untagged-variants)
+* [Blog post introducing untagged variants](/blog/improving-interop)
+* [Unboxed record](/docs/manual/v10.0.0/unboxed)

pages/docs/manual/latest/interop-cheatsheet.mdx

@@ -45,7 +45,7 @@ This is a glossary with examples. All the features are described by later pages.
 - [`@JSX`](jsx)
 - `@react.component`: [here](/docs/react/latest/introduction) and [here](https://github.com/reasonml/reason-react)
 - [`@warning`](attribute#usage)
-- [`@unboxed`](unboxed)
+- [`@unboxed`](variant#untagged-variants)
 
 ### Extension Points