proper json in pipelines

Exercise-Configuration.md

@@ -237,9 +237,9 @@ Mandatory items are bold, optional italic, description of items follows:
 Example:
 
 ```
-[
+{
-   { "variables":[] },
+   "variables":[],
-   { "boxes": [
+   "boxes": [
       {
          "name":"source",
          "portsIn":[],
@@ -276,8 +276,8 @@ Example:
          "portsOut":[{ "score":[{"type":"file", "value":"score"}] }],
          "type":"evaluation"
       }
-   ] }
    ]
+}
 ```
 
 ## Limits