Fix example responses for Project Issue Board creation API in the docs

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

changelogs/unreleased/fix-api-boards-docs.yml

+---
+title: Fix example responses for Project Issue Board creation API in the docs
+merge_request: 46749
+author: Takuya Noguchi
+type: fixed

doc/api/boards.md

@@ -203,48 +203,12 @@ Example response:
       "web_url": "http://example.com/diaspora/diaspora-project-site"
     },
     "name": "newboard",
-    "milestone":   {
-      "id": 12
-      "title": "10.0"
-    },
-    "lists" : [
-      {
-        "id" : 1,
-        "label" : {
-          "name" : "Testing",
-          "color" : "#F0AD4E",
-          "description" : null
-        },
-        "position" : 1,
-        "max_issue_count": 0,
-        "max_issue_weight": 0,
-        "limit_metric":  null
-      },
-      {
-        "id" : 2,
-        "label" : {
-          "name" : "Ready",
-          "color" : "#FF0000",
-          "description" : null
-        },
-        "position" : 2,
-        "max_issue_count": 0,
-        "max_issue_weight": 0,
-        "limit_metric":  null
-      },
-      {
-        "id" : 3,
-        "label" : {
-          "name" : "Production",
-          "color" : "#FF5F00",
-          "description" : null
-        },
-        "position" : 3,
-        "max_issue_count": 0,
-        "max_issue_weight": 0,
-        "limit_metric":  null
-      }
-    ]
+    "lists" : [],
+    "group": null,
+    "milestone": null,
+    "assignee" : null,
+    "labels" : [],
+    "weight" : null
   }
 ```