doc: remove the buffer example using Symbol.toPrimitive

The single buffer API is the only one supporting Symbol.toPrimitive
but ideally it should not be used. Remove the documentation to
prevent users from potentially using this API.

doc/api/buffer.md

@@ -884,15 +884,18 @@ appropriate for `Buffer.from()` variants.
 
 ### Class Method: `Buffer.from(object[, offsetOrEncoding[, length]])`
 <!-- YAML
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/27051
+    description: Dropped support for `Symbol.toPrimitive`.
 added: v8.2.0
 -->
 
-* `object` {Object} An object supporting `Symbol.toPrimitive` or `valueOf()`.
+* `object` {Object} An object supporting `valueOf()`.
 * `offsetOrEncoding` {integer|string} A byte-offset or encoding, depending on
-  the value returned either by `object.valueOf()` or
-  `object[Symbol.toPrimitive]()`.
-* `length` {integer} A length, depending on the value returned either by
-  `object.valueOf()` or `object[Symbol.toPrimitive]()`.
+  the value returned by `object.valueOf()`.
+* `length` {integer} A length, depending on the value returned by
+  `object.valueOf()`.
 
 For objects whose `valueOf()` function returns a value not strictly equal to
 `object`, returns `Buffer.from(object.valueOf(), offsetOrEncoding, length)`.
@@ -902,20 +905,6 @@ const buf = Buffer.from(new String('this is a test'));
 // Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>
 ```
 
-For objects that support `Symbol.toPrimitive`, returns
-`Buffer.from(object[Symbol.toPrimitive](), offsetOrEncoding, length)`.
-
-```js
-class Foo {
-  [Symbol.toPrimitive]() {
-    return 'this is a test';
-  }
-}
-
-const buf = Buffer.from(new Foo(), 'utf8');
-// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>
-```
-
 A `TypeError` will be thrown if `object` has not mentioned methods or is not of
 other type appropriate for `Buffer.from()` variants.