boost version 1.86 support

Added fix for boost::asio::spawn overload issue reported similar
to chriskohlhoff/asio#1524.  This error is reported by telemetry
recipe during Boost 1.86 migration build.

Error details

'''
  tmp/work/armv7ahf-vfpv4d16-openbmc-linux-gnueabi/telemetry/1.0+git/
  recipe-sysroot/usr/include/sdbusplus/asio/object_server.hpp:238:27:
  error: call of overloaded 'spawn
'''

Proposed fix is to use default completion token.

Tested: verified build

Change-Id: I4c24869c1467a04ac40027bc4c50aebd1f3acb78
Signed-off-by: Jayanth Othayoth <ojayanth@gmail.com>
diff --git a/include/sdbusplus/asio/object_server.hpp b/include/sdbusplus/asio/object_server.hpp
index 6275d46..4f42cc9 100644
--- a/include/sdbusplus/asio/object_server.hpp
+++ b/include/sdbusplus/asio/object_server.hpp
@@ -235,7 +235,9 @@
         message_t b{m};
 
         // spawn off a new coroutine to handle the method call
-        boost::asio::spawn(io_, std::bind_front(&self_t::after_spawn, this, b));
+        boost::asio::spawn(io_, std::bind_front(&self_t::after_spawn, this, b),
+                           {});
+
         return 1;
     }