Fix minor documentation error

[remyzandwijk]

There is an error in the v4 documentation. This example is given:

<button hx-post="/clicked"
        hx-trigger="click"
        hx-target="#output"
        hx-swap="outerHTML">
    Click Me
</button>
<output id="output"></output>

The documentation states that the button is replaced when the button is clicked, but that is obviously not true. The complete <output id="output"></output> block is being replaced.