Hide fiddle completely using single comment block

[bahmutov]

We should be able to hide the fiddle's code completely by hiding it in the HTML comment block

Instead of

<!-- fiddle Initial -->
```js
cy.visit('/')
cy.get('input').should('be.visible')
cy.screenshot('initial')
```
<!-- fiddle-end -->

Do

<!-- fiddle Initial
```js
cy.visit('/')
cy.get('input').should('be.visible')
cy.screenshot('initial')
```
-->