Update mistralai.ipynb (#28440)

Just fixing a broken link

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---------

Co-authored-by: ccurme <chester.curme@gmail.com>

docs/docs/integrations/chat/mistralai.ipynb

@@ -39,7 +39,7 @@
     "### Credentials\n",
     "\n",
     "\n",
-    "A valid [API key](https://console.mistral.ai/users/api-keys/) is needed to communicate with the API. Once you've done this set the MISTRAL_API_KEY environment variable:"
+    "A valid [API key](https://console.mistral.ai/api-keys/) is needed to communicate with the API. Once you've done this set the MISTRAL_API_KEY environment variable:"
    ]
   },
   {