fix: move Custom Transcriber to top level and rename Custom TTS

- Moved "Custom Transcriber" from Model configurations section to top level,
  next to Custom voices
- Renamed "Custom TTS integration" to "Custom TTS"

Co-Authored-By: Claude <noreply@anthropic.com>

Author: vapi-tasker[bot]

fern/docs.yml

@@ -168,8 +168,6 @@ navigation:
                 path: openai-realtime.mdx
               - page: Provider keys
                 path: customization/provider-keys.mdx
-              - page: Custom transcriber
-                path: customization/custom-transcriber.mdx
           - section: Tools
             path: tools/introduction.mdx
             collapsed: true
@@ -241,7 +239,10 @@ navigation:
                 path: customization/custom-voices/elevenlabs.mdx
               - page: PlayHT
                 path: customization/custom-voices/playht.mdx
-          - page: Custom TTS integration
+          - page: Custom transcriber
+            path: customization/custom-transcriber.mdx
+            icon: fa-light fa-microphone
+          - page: Custom TTS
             path: customization/custom-tts.mdx
             icon: fa-light fa-volume-high
           - section: Custom LLMs