http.HTTPConnection.putheader tweak (#10978)

stdlib/http/client.pyi

@@ -176,7 +176,7 @@ class HTTPConnection:
     def connect(self) -> None: ...
     def close(self) -> None: ...
     def putrequest(self, method: str, url: str, skip_host: bool = False, skip_accept_encoding: bool = False) -> None: ...
-    def putheader(self, header: str, *argument: str) -> None: ...
+    def putheader(self, header: str | bytes, *argument: str | bytes) -> None: ...
     def endheaders(self, message_body: _DataType | None = None, *, encode_chunked: bool = False) -> None: ...
     def send(self, data: _DataType | str) -> None: ...