MINOR: server: fix doc/trace on lb algo for dynamic server creation

The text mentionned that only backends with consistent hash method were
supported for dynamic servers. In fact, it is only required that the lb
algorith is dynamic.
diff --git a/src/server.c b/src/server.c
index 6728e11..60e76a6 100644
--- a/src/server.c
+++ b/src/server.c
@@ -4352,7 +4352,7 @@
 		return cli_err(appctx, "No such backend.");
 
 	if (!(be->lbprm.algo & BE_LB_PROP_DYN)) {
-		cli_err(appctx, "Backend must use a consistent hashing method for load balancing to support dynamic servers.");
+		cli_err(appctx, "Backend must use a dynamic load balancing to support dynamic servers.");
 		return 1;
 	}