#18044: Fix parsing of encoded words of the form =?utf8?q?=XX...?=

The problem was I was only checking for decimal digits after the third '?',
not for *hex* digits :(.

This changeset also fixes a couple of comment typos, deletes an unused
function relating to encoded word parsing, and removed an invalid
'if' test from the folding function that was revealed by the tests
written to validate this issue.

Lib/test/test_email/test__header_value_parser.py

@@ -170,6 +170,15 @@ class TestParser(TestParserMixin, TestEmailBase):
                         [],
                         '')
 
+    def test_get_encoded_word_quopri_utf_escape_follows_cte(self):
+        # Issue 18044
+        self._test_get_x(parser.get_encoded_word,
+                        '=?utf-8?q?=C3=89ric?=',
+                        'Éric',
+                        'Éric',
+                        [],
+                        '')
+
     # get_unstructured
 
     def _get_unst(self, value):