doc: update similarity threshold to 0.75 and note (#770)

Author: Pouyanpi

docs/user_guides/configuration-guide.md

@@ -706,13 +706,13 @@ rails:
       # Whether to use only the embeddings when interpreting the user's message
       embeddings_only: True
       # Use only the embeddings when the similarity is above the specified threshold.
-      embeddings_only_similarity_threshold: 0.5
+      embeddings_only_similarity_threshold: 0.75
       # When the fallback is set to None, if the similarity is below the threshold, the user intent is computed normally using the LLM.
       # When it is set to a string value, that string value will be used as the intent.
       embeddings_only_fallback_intent: None
 ```
 
-**IMPORTANT**: This is recommended only when enough examples are provided.
+**IMPORTANT**: This is recommended only when enough examples are provided. The threshold used here is 0.75, which triggers an LLM call for user intent generation if the similarity is below this value. If you encounter false positives, consider increasing the threshold to 0.8. Note that the threshold is model dependent.
 
 ## Exceptions