CLEANUP: conn-stream: Don't export conn-stream pool

There is no reason to export the conn-stream pool.
diff --git a/include/haproxy/conn_stream.h b/include/haproxy/conn_stream.h
index a89104b..730a29b 100644
--- a/include/haproxy/conn_stream.h
+++ b/include/haproxy/conn_stream.h
@@ -27,13 +27,10 @@
 #include <haproxy/connection.h>
 #include <haproxy/conn_stream-t.h>
 #include <haproxy/obj_type.h>
-#include <haproxy/pool-t.h>
 
 struct stream;
 struct check;
 
-extern struct pool_head *pool_head_connstream;
-
 #define IS_HTX_CS(cs)     (cs_conn(cs) && IS_HTX_CONN(cs_conn(cs)))
 
 struct conn_stream *cs_new(enum obj_type *endp, void *ctx, enum obj_type *app, void *data, const struct data_cb *data_cb);