CLEANUP: conn-stream: Remove cs_applet_shut declaration from header file

This function was renamed and moved in applet code. cs_applet_shut() does
not exist anymore. Its declaration must be removed.
diff --git a/include/haproxy/conn_stream.h b/include/haproxy/conn_stream.h
index 4a567a5..cfc8a49 100644
--- a/include/haproxy/conn_stream.h
+++ b/include/haproxy/conn_stream.h
@@ -50,8 +50,6 @@
 int cs_reset_endp(struct conn_stream *cs);
 
 struct appctx *cs_applet_create(struct conn_stream *cs, struct applet *app);
-void cs_applet_shut(struct conn_stream *cs);
-
 /* Returns the endpoint target without any control */
 static inline void *__cs_endp_target(const struct conn_stream *cs)
 {