rest-api-groups.txt: Correct input examples to use [] for lists

Change-Id: I109bced2f9309dd20a7962d5fdbcd999fa6f87ff
(cherry picked from commit a2bf824fa154b7cb51e8f89df8321d02c25f3425)
diff --git a/Documentation/rest-api-groups.txt b/Documentation/rest-api-groups.txt
index 2f73fc7..0779579 100644
--- a/Documentation/rest-api-groups.txt
+++ b/Documentation/rest-api-groups.txt
@@ -1008,10 +1008,10 @@
   Content-Type: application/json;charset=UTF-8
 
   {
-    "groups": {
+    "groups": [
       "MyGroup",
       "MyOtherGroup"
-    }
+    ]
   }
 ----
 
@@ -1090,10 +1090,10 @@
   Content-Type: application/json;charset=UTF-8
 
   {
-    "members": {
+    "members": [
       "MyGroup",
       "MyOtherGroup"
-    }
+    ]
   }
 ----