fix(docs): drop openapi: from Trading + Orders & Positions groups

The shadow MDX pages array already enumerates the toggle pages; the
openapi: spec reference was causing Mintlify to auto-inject every
operation in openapi.json under those groups, polluting the sidebar
with 'API Reference / Local Only / Hosted / Data Feeds' sub-groups
below the 11 shadow MDX pages.

Author: realfishsam

docs/docs.json

@@ -176,8 +176,7 @@
               "api-reference/buildOrder",
               "api-reference/submitOrder",
               "api-reference/cancelOrder"
-            ],
-            "openapi": "api-reference/openapi.json"
+            ]
           },
           {
             "group": "Orders & Positions",
@@ -189,8 +188,7 @@
               "api-reference/fetchAllOrders",
               "api-reference/fetchPositions",
               "api-reference/fetchBalance"
-            ],
-            "openapi": "api-reference/openapi.json"
+            ]
           },
           {
             "group": "Realtime",