Fix map example in doc/spec (#952)

diff --git a/doc/src/content/xdocs/spec.xml b/doc/src/content/xdocs/spec.xml
index 94fa68e..2cf3f8a 100644
--- a/doc/src/content/xdocs/spec.xml
+++ b/doc/src/content/xdocs/spec.xml
@@ -222,7 +222,7 @@
     <source>
 {
   "type": "map",
-  "items" : "long",
+  "values" : "long",
   "default": {}
 }
     </source>