fix(utils/get-selector): ignore 'xmlns' attribute when generating a selector (#4303)

Ignore the "xmlns" attribute when generating a selector, since the
selector spec does not support namespaces.

Closes: #4302

Author: thuey

lib/core/utils/get-selector.js

@@ -22,7 +22,8 @@ const ignoredAttributes = [
   'aria-expanded',
   'aria-grabbed',
   'aria-pressed',
-  'aria-valuenow'
+  'aria-valuenow',
+  'xmlns'
 ];
 const MAXATTRIBUTELENGTH = 31;
 const attrCharsRegex = /([\\"])/g;

test/core/utils/get-selector.js

@@ -471,7 +471,8 @@ describe('axe.utils.getSelector', function () {
       'aria-expanded',
       'aria-grabbed',
       'aria-pressed',
-      'aria-valuenow'
+      'aria-valuenow',
+      'xmlns'
     ];
     ignoredAttributes.forEach(function (att) {
       node.setAttribute(att, 'true');