qapi/parser: Fix type hints

Fixes: 3e32dca (qapi: Rewrite parsing of doc comment section symbols and tags)
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20230511111709.971477-1-armbru@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

scripts/qapi/parser.py

@@ -563,11 +563,11 @@ def end_comment(self) -> None:
         self._switch_section(QAPIDoc.NullSection(self._parser))
 
     @staticmethod
-    def _match_at_name_colon(string: str) -> re.Match:
+    def _match_at_name_colon(string: str) -> Optional[re.Match[str]]:
         return re.match(r'@([^:]*): *', string)
 
     @staticmethod
-    def _match_section_tag(string: str) -> re.Match:
+    def _match_section_tag(string: str) -> Optional[re.Match[str]]:
         return re.match(r'(Returns|Since|Notes?|Examples?|TODO): *', string)
 
     def _append_body_line(self, line: str) -> None: