Adds prereq to trim messages (#5844)

docs/core_docs/docs/how_to/trim_messages.ipynb

@@ -7,8 +7,18 @@
    "source": [
     "# How to trim messages\n",
     "\n",
-    ":::note\n",
-    "The `trimMessages` function is available in `@langchain/core` version `0.2.8` and above.\n",
+    ":::info Prerequisites\n",
+    "\n",
+    "This guide assumes familiarity with the following concepts:\n",
+    "\n",
+    "- [Messages](/docs/concepts/#messages)\n",
+    "- [Chat models](/docs/concepts/#chat-models)\n",
+    "- [Chaining](/docs/how_to/sequence/)\n",
+    "- [Chat history](/docs/concepts/#chat-history)\n",
+    "\n",
+    "The methods in this guide also require `@langchain/core>=0.2.8`.\n",
+    "Please see here for a [guide on upgrading](/docs/how_to/installation/#installing-integration-packages).\n",
+    "\n",
     ":::\n",
     "\n",
     "All models have finite context windows, meaning there's a limit to how many tokens they can take as input. If you have very long messages or a chain/agent that accumulates a long message is history, you'll need to manage the length of the messages you're passing in to the model.\n",