ssl_stream: fix ambiguous async_teardown

We are observing the following in openbmc/bmcweb with clang-16.

```
/usr/local/include/boost/beast/websocket/impl/read.hpp:695:17: error: call to 'async_teardown' is ambiguous
```

This was reported in boostorg#2648 and this change was suggested
as a fix.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>

include/boost/beast/ssl/ssl_stream.hpp

@@ -673,7 +673,7 @@ class ssl_stream
         ssl_stream<SyncStream>& stream,
         boost::system::error_code& ec);
 
-    template<class AsyncStream, BOOST_BEAST_ASYNC_TPARAM1 TeardownHandler>
+    template<class AsyncStream, class TeardownHandler>
     friend
     void
     async_teardown(
@@ -697,7 +697,7 @@ teardown(
 }
 
 template<class AsyncStream,
-        BOOST_BEAST_ASYNC_TPARAM1 TeardownHandler = net::default_completion_token_t<beast::executor_type<AsyncStream>>>
+        class TeardownHandler = net::default_completion_token_t<beast::executor_type<AsyncStream>>>
 void
 async_teardown(
     boost::beast::role_type role,