doc: move history entry to class description

Move the history entry for the `TextDecoder` class into the class
description itself instead of its constructor.

Refs: nodejs#55938

Author: lpinca

doc/api/util.md

@@ -1998,6 +1998,10 @@ The full list of formats can be found in [modifiers][].
 
 <!-- YAML
 added: v8.3.0
+changes:
+  - version: v11.0.0
+    pr-url: https://github.com/nodejs/node/pull/22281
+    description: The class is now available on the global object.
 -->
 
 An implementation of the [WHATWG Encoding Standard][] `TextDecoder` API.
@@ -2076,14 +2080,6 @@ is not supported.
 
 ### `new TextDecoder([encoding[, options]])`
 
-<!-- YAML
-added: v8.3.0
-changes:
-  - version: v11.0.0
-    pr-url: https://github.com/nodejs/node/pull/22281
-    description: The class is now available on the global object.
--->
-
 * `encoding` {string} Identifies the `encoding` that this `TextDecoder` instance
   supports. **Default:** `'utf-8'`.
 * `options` {Object}