[PATCH v2 0/2] MR9056: msxml3/element: Implement removeAttributeNode function.

[Reinhold Gschweicher (＠neroburner)]

Implement the function `IXMLDOMElement_removeAttributeNode`. Essentially
pass the hard work to `IXMLDOMNamedNodeMap_removeNamedItem`.

Use the fact, that attribute names are unique in elements.

One case that isn't checked is wheter or not the value of the provided
attribute match with the one stored in the dom-element.

This MR implements according to the tests introduced in https://gitlab.winehq.org/wine/wine/-/merge_requests/8928

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  v2: msxml3/element: do attribute removal ourselfs

https://gitlab.winehq.org/wine/wine/-/merge_requests/9056