build error because of discard const qualifiers

[vipcxj]

error: passing ‘const asiochan::basic_channel<void, 0, asio::any_io_executor>’ as ‘this’ argument discards qualifiers [-fpermissive]
[build]    22 |             return &channel.shared_state() == shared_state_;
[build]       |                     ~~~~~~~~~~~~~~~~~~~~^~

I have fixed it, I will submit a pr.