add missing noun (#1010)

## Description

<!-- describe the changes as bullet points -->

- "for a long and has already" - I did a double take 😂 and realized it was missing the word "time"

## Testing Steps

- [ ] Run the app locally using `fern docs dev` or navigate to preview deployment
- [ ] Ensure that the changed pages and code snippets work

Author: cellog

fern/customization/speech-configuration.mdx

@@ -77,7 +77,7 @@ This plan defines the parameters for when the assistant begins speaking after th
 - **Transcription-Based Detection**: Customize how the assistant determines that the customer has stopped speaking based on what they're saying. This offers more control over the timing. **Example:** When a customer says, "My account number is 123456789, I want to transfer $500."
   - The system detects the number "123456789" and waits for 0.5 seconds (`WaitSeconds`) to ensure the customer isn't still speaking.
   - If the customer were to finish with an additional line, "I want to transfer $500.", the system uses `onPunctuationSeconds` to confirm the end of the speech and then proceed with the request processing.
-  - In a scenario where the customer has been silent for a long and has already finished speaking but the transcriber is not confident to punctuate the transcription, `onNoPunctuationSeconds` is used for 1.5 seconds.
+  - In a scenario where the customer has been silent for a long time and has already finished speaking but the transcriber is not confident to punctuate the transcription, `onNoPunctuationSeconds` is used for 1.5 seconds.
 
 ## Stop Speaking Plan