Remove dead link

This was moved to the operations guide.

docs/administration-guide/start.md

@@ -18,7 +18,6 @@ Are you in charge of managing Metabase for your organization? Then you're in the
 * [Sharing dashboards and questions with public links](12-public-links.md)
 * [Embedding Metabase in other Applications](13-embedding.md)
 * [Caching query results](14-caching.md)
-* [Enable performance monitoring](15-enable-jmx.md)
 
 First things first, you'll need to install Metabase. If you haven’t done that yet, our [Installation Guide](../operations-guide/start.md#installing-and-running-metabase) will help you through the process.