Update all URLs to langchain docunotebooks (#1745)

docs/docs/tutorials/plan-and-execute/plan-and-execute.ipynb

@@ -102,7 +102,7 @@
    "source": [
     "## Define Tools\n",
     "\n",
-    "We will first define the tools we want to use. For this simple example, we will use a built-in search tool via Tavily. However, it is really easy to create your own tools - see documentation [here](https://python.langchain.com/v0.2/docs/how_to/custom_tools) on how to do that."
+    "We will first define the tools we want to use. For this simple example, we will use a built-in search tool via Tavily. However, it is really easy to create your own tools - see documentation [here](https://python.langchain.com/docs/how_to/custom_tools) on how to do that."
    ]
   },
   {