Refactor: Update custom keywords to keyterm prompting

Co-authored-by: sahil <sahil@vapi.ai>

Author: cursoragent

fern/customization/custom-keywords.mdx

@@ -1,6 +1,6 @@
 ---
-title: Custom Keywords
-subtitle: Enhanced transcription accuracy guide
+title: Deepgram Keywords and Keyterm Prompting
+subtitle: Boost STT accuracy for domain words and phrases
 slug: customization/custom-keywords
 ---
 
@@ -21,6 +21,11 @@ Keyword boosting is beneficial for:
 - Use single words for `keywords` (no spaces or punctuation). For multi-word phrases, use `keyterm` instead.
 - Custom model training is the most effective way to ensure accurate keyword recognition when you need extensive vocabulary coverage.
 
+### Model support
+
+- Keywords is available on Deepgram Nova-2, Nova-1, Enhanced, and Base speech-to-text models.
+- For Nova-3 models, use Keyterm Prompting instead of Keywords.
+
 ## Enabling Keyword Boosting in Vapi
 
 ### API Call Integration