docs[patch]: moved `vectorstore` notebook file (#14181)

The `/docs/integrations/toolkits/vectorstore` page is not the
Integration page. The best place is in `/docs/modules/agents/how_to/`
- Moved the file
- Rerouted the page URL

docs/vercel.json

@@ -1056,6 +1056,10 @@
       "source": "/en/latest/modules/agents/agents/custom_agent.html",
       "destination": "/docs/modules/agents/how_to/custom_agent"
     },
+    {
+      "source": "/docs/integrations/toolkits/vectorstore",
+      "destination": "/docs/modules/agents/how_to/vectorstore"
+    },
     {
       "source": "/en/latest/modules/agents/agents/custom_agent_with_tool_retrieval.html",
       "destination": "/docs/modules/agents/how_to/custom_agent_with_tool_retrieval"