zuul.yaml: Change Job.nodes to nodeset

Change-Id: I6ba40f21778d918b56e8e16fe0163599d141e4ec
diff --git a/.zuul.yaml b/.zuul.yaml
index b0fe135..b6612ae 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -16,7 +16,7 @@
 - job:
     name: zuul-stream-functional
     parent: multinode
-    nodes: zuul-functional
+    nodeset: zuul-functional
     pre-run: playbooks/zuul-stream/pre
     run: playbooks/zuul-stream/functional
     post-run: