Update about.mdx

Points to updated server.schema.json location.

Author: jonathansampson

docs/registry/about.mdx

@@ -16,7 +16,7 @@ The MCP Registry provides:
 - A REST API for MCP clients and aggregators to discover available servers
 - Standardized installation and configuration information
 
-Server metadata is stored in a standardized [`server.json` format](https://github.com/modelcontextprotocol/registry/blob/main/docs/reference/server-json/server.schema.json), which contains:
+Server metadata is stored in a standardized [`server.json` format](https://github.com/modelcontextprotocol/registry/blob/main/docs/reference/server-json/draft/server.schema.json), which contains:
 
 - The server's unique name (e.g., `io.github.user/server-name`)
 - Where to locate the server (e.g., npm package name, remote server URL)