Remove inheritable overriden groups attributes

===

<svg xmlns="http://www.w3.org/2000/svg">
    <g attr1="val1">
        <g fill="red">
            <path fill="green" d="..."/>
        </g>
        <path d="..."/>
    </g>
</svg>

@@@

<svg xmlns="http://www.w3.org/2000/svg">
    <g attr1="val1">
        <path fill="green" d="..."/>
        <path d="..."/>
    </g>
</svg>