email: test case for blank between nested comment

To test a whitespace between two nested comments leads to a
new line with one space indentation on folding

Author: beledouxdenis

Lib/test/test_email/test__header_value_parser.py

@@ -3310,6 +3310,8 @@ def test_address_list_with_long_unwrapable_comment(self):
              '(Escaped \\( \\) chars \\\\ in comments stay\n escaped)<spy@example.org>\n'),
             ('((loremipsum)(loremipsum)(loremipsum)(loremipsum))<spy@example.org>',
              '((loremipsum)(loremipsum)(loremipsum)(loremipsum))<spy@example.org>\n'),
+            ('((loremipsum)(loremipsum)(loremipsum) (loremipsum))<spy@example.org>',
+             '((loremipsum)(loremipsum)(loremipsum)\n (loremipsum))<spy@example.org>\n'),
         ]
         for (to, folded) in cases:
             with self.subTest(to=to):