doc: use cjs as block code's type in MockTimers

Use `cjs` instead of `js` to show toggle button between
CJS and ESM because corresponding example using `mjs`
exists.

PR-URL: nodejs/node#49309
Reviewed-By: Geoffrey Booth <[email protected]>
Reviewed-By: Antoine du Hamel <[email protected]>
Reviewed-By: Chemi Atlow <[email protected]>
Reviewed-By: Raz Luvaton <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>

graal-nodejs/doc/api/test.md

@@ -1545,7 +1545,7 @@ import { mock } from 'node:test';
 mock.timers.enable(['setInterval']);
 ```
 
-```js
+```cjs
 const { mock } = require('node:test');
 mock.timers.enable(['setInterval']);
 ```
@@ -1582,7 +1582,7 @@ import { mock } from 'node:test';
 mock.timers.reset();
 ```
 
-```js
+```cjs
 const { mock } = require('node:test');
 mock.timers.reset();
 ```
@@ -1631,7 +1631,7 @@ test('mocks setTimeout to be executed synchronously without having to actually w
 });
 ```
 
-```js
+```cjs
 const assert = require('node:assert');
 const { test } = require('node:test');
 
@@ -1670,7 +1670,7 @@ test('mocks setTimeout to be executed synchronously without having to actually w
 });
 ```
 
-```js
+```cjs
 const assert = require('node:assert');
 const { test } = require('node:test');
 
@@ -1714,7 +1714,7 @@ test('mocks setTimeout to be executed synchronously without having to actually w
 });
 ```
 
-```js
+```cjs
 const assert = require('node:assert');
 const { test } = require('node:test');
 
@@ -1771,7 +1771,7 @@ test('mocks setTimeout to be executed synchronously without having to actually w
 });
 ```
 
-```js
+```cjs
 const assert = require('node:assert');
 const { test } = require('node:test');
 const nodeTimers = require('node:timers');
@@ -1833,7 +1833,7 @@ test('should tick five times testing a real use case', async (context) => {
 });
 ```
 
-```js
+```cjs
 const assert = require('node:assert');
 const { test } = require('node:test');
 const nodeTimersPromises = require('node:timers/promises');
@@ -1899,7 +1899,7 @@ test('runAll functions following the given order', (context) => {
 });
 ```
 
-```js
+```cjs
 const assert = require('node:assert');
 const { test } = require('node:test');