doc: split example into two

This makes sure the "good" and "bad" examples are split into two.
Otherwise it'll result in an parse error.

PR-URL: https://github.com/nodejs/node/pull/27670
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Refael Ackermann (רפאל פלחי) <refack@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>

doc/api/cli.md

@@ -218,15 +218,11 @@ or be removed in the future.
 
 To avoid these cases, any builtin function overrides should be defined upfront:
 
-<!-- eslint-disable no-redeclare -->
 ```js
 const o = {};
 // THROWS: Cannot assign read only property 'toString' of object
 o.toString = () => 'string';
 
-// OK
-const o = { toString: () => 'string' };
-
 class X {
   constructor() {
     this.toString = () => 'string';
@@ -234,6 +230,11 @@ class X {
 }
 // THROWS: Cannot assign read only property 'toString' of object
 new X();
+```
+
+```js
+// OK
+const o = { toString: () => 'string' };
 
 class X {
   toString = undefined;