Fix broken link in Mixpanel migration guide

- Changed /data-warehouse-ingestion/overview to /data-warehouse-ingestion/introduction
- Resolves build failure caused by non-existent page reference

Author: shubhamstatsig

docs/guides/migrate-from-mixpanel.mdx

@@ -93,7 +93,7 @@ Once your data looks like Statsig events, you can start bringing them in:
 | If you exported from Mixpanel via... | Import into Statsig using... | Best when... |
 |--------------------------------------|------------------------------|--------------|
 | S3 export | [S3 ingestion](/data-warehouse-ingestion/s3) | You're backfilling large datasets |
-| Warehouse (Snowflake/BigQuery/Redshift) | [Warehouse ingestion](/data-warehouse-ingestion/overview) | Your Mixpanel data already lives in a warehouse |
+| Warehouse (Snowflake/BigQuery/Redshift) | [Warehouse ingestion](/data-warehouse-ingestion/introduction) | Your Mixpanel data already lives in a warehouse |
 | Export API | [Event Webhook](https://docs.statsig.com/http-api#post-event-webhook) | You're moving a few days/weeks of data programmatically |
 | CSV download | [Event Webhook](https://docs.statsig.com/http-api#post-event-webhook) | You're testing or moving a small slice of data |