docs: tests/standard tests api ref redirect (#29444)

docs/vercel.json

@@ -137,6 +137,10 @@
     {
       "source": "/api_reference/mongodb/:path(.*/?)*",
       "destination": "https://langchain-mongodb.readthedocs.io/en/latest/langchain_mongodb/api_docs.html"
+    },
+    {
+      "source": "/api_reference/tests/:path(.*/?)*",
+      "destination": "/api_reference/standard_tests/:path"
     }
   ]
 }