Fix docblock to solve phpstan errors when passing an array to html()->div()

[SanderMuller]

Fixes the following phpstan error:

Parameter #1 $contents of method Spatie\Html\Html::div() expects               
         Spatie\Html\HtmlElement|string|null, array<int, Spatie\Html\Elements\Element>  
         given.      

for the given code:

html()->div([
    html()->p('example'),
    html()->p('second child'),
]);

This PR updates the docblock of div (html()->div()) to match the types of BaseElement::children() since it just forwards to that function.

[freekmurze]

Thanks!