docs: update ragas_custom_model.ipynb (#988)

avaialble -> available

Author: eltociear

docs/howtos/customisations/ragas_custom_model.ipynb

@@ -10,7 +10,7 @@
     "1. Generation of QA pairs, evolution, etc\n",
     "2. LLM as Critic model to give feedback to generated QA pairs to ensure and improve quality\n",
     "\n",
-    "We have built and opensourced a [custom model](https://huggingface.co/explodinggradients/Ragas-critic-llm-Qwen1.5-GPTQ) as critic model to be used instead of GPT-4 (default). This model is avaialble here for free and can deliver upto 200 tokens per second of an A10 instance. \n",
+    "We have built and opensourced a [custom model](https://huggingface.co/explodinggradients/Ragas-critic-llm-Qwen1.5-GPTQ) as critic model to be used instead of GPT-4 (default). This model is available here for free and can deliver upto 200 tokens per second of an A10 instance. \n",
     "\n",
     "Follow the rest of the notebook to use this model as critic model instead of GPT-4.\n"
    ]