bpo-30442: Skips refcount test in test_xml_etree under coverage (#1767) (#3363)

(cherry picked from commit 1de4705)

Author: vstinner

Lib/test/test_xml_etree.py

@@ -1523,6 +1523,7 @@ def test_bug_xmltoolkit62(self):
         self.assertEqual(t.find('.//paragraph').text,
             'A new cultivar of Begonia plant named \u2018BCT9801BEG\u2019.')
 
+    @unittest.skipIf(sys.gettrace(), "Skips under coverage.")
     def test_bug_xmltoolkit63(self):
         # Check reference leak.
         def xmltoolkit63():