erp5_svg_editor: force removal of extra attributes

Otherwise, a weird behaviour is observed with compound attributes (eg.
`xmlns:inkscape`), where the second part of the attribute is replaced by
`undefined`, giving a wrong SVG file when there are multiple attributes
(duplicate attribute).

bt5/erp5_svg_editor/SkinTemplateItem/portal_skins/erp5_svg_editor/method-draw/js/sanitize.js.js

@@ -183,9 +183,7 @@ svgedit.sanitize.sanitizeSvg = function(node) {
           se_attrs.push([attrName, attr.nodeValue]);
         } 
 
-        // TODO looks dangerous
-
-        //node.removeAttributeNS(attrNsURI, attrLocalName);
+        node.removeAttributeNS(attrNsURI, attrLocalName);
       }
       
       // Add spaces before negative signs where necessary