fix typo in variable name (closes #21586)

Doc/howto/sockets.rst

@@ -210,7 +210,7 @@ length message::
                chunk = self.sock.recv(min(MSGLEN - bytes_recd, 2048))
                if chunk == b'':
                    raise RuntimeError("socket connection broken")
-               chucks.append(chunk)
+               chunks.append(chunk)
                bytes_recd = bytes_recd + len(chunk)
            return b''.join(chunks)