Fix typo in hyde.ipynb (#688)

therefor -> therefore

docs/modules/utils/combine_docs_examples/hyde.ipynb

@@ -10,7 +10,7 @@
     "\n",
     "At a high level, HyDE is an embedding technique that takes queries, generates a hypothetical answer, and then embeds that generated document and uses that as the final example. \n",
     "\n",
-    "In order to use HyDE, we therefor need to provide a base embedding model, as well as an LLMChain that can be used to generate those documents. By default, the HyDE class comes with some default prompts to use (see the paper for more details on them), but we can also create our own."
+    "In order to use HyDE, we therefore need to provide a base embedding model, as well as an LLMChain that can be used to generate those documents. By default, the HyDE class comes with some default prompts to use (see the paper for more details on them), but we can also create our own."
    ]
   },
   {