https://github.com/boostorg/signals2/issues/70

From 4d994bbed820882059c7842ba5e230a26d68f2f0 Mon Sep 17 00:00:00 2001
From: Frank Mori Hess <fmh6jj@gmail.com>
Date: Sat, 30 Dec 2023 14:51:49 -0500
Subject: [PATCH] Fix disconnect by slot when slot is wrapped in a
 boost::reference_wrapper

--- a/boost/signals2/detail/signal_template.hpp
+++ b/boost/signals2/detail/signal_template.hpp
@@ -223,7 +223,7 @@ namespace boost
         void disconnect(const T &slot)
         {
           typedef mpl::bool_<(is_convertible<T, group_type>::value)> is_group;
-          do_disconnect(slot, is_group());
+          do_disconnect(unwrap_ref(slot), is_group());
         }
         // emit signal
         result_type operator ()(BOOST_SIGNALS2_SIGNATURE_FULL_ARGS(BOOST_SIGNALS2_NUM_ARGS))