Remove "charset=utf-8" of download of xml file out of js chrome extension

Question

I am programming a extension for chrome for my company. I am creating a XML file out of a API request. The XML file is used for an import, and the program that gets the import, doesn't like the charset=utf-8 at the beginning of the XML (see short XML below).

charset=utf-8
<xml>
    xml data
</xml>

I have to manually remove the charset=utf-8 and it works. Below you find the js code for the download. I do not add the charset=utf-8 manually. It must be in that code, but I don't find the problem.

var filename = prompt('Enter file name:', 'XML_file_export');
var downloadPath = prompt('Enter download path:', 'XML_export');
chrome.downloads.download({url:'data:text/xml,charset=utf-8' + encodeURIComponent(xmlData), filename: downloadPath + filename});

Please can someone help me to remove that charset=utf-8 at the beginning of the XML file. It is the first time that I work with this and I haven't found any information about that.

I've tried to remove that charset=utf-8 from the chrome.downloads.download, but than it wasn't downloading. Also I have tried without the encodeURIComponent but it also haven't worked.