Fix schema.json path reference in registry docs (#1734)

Update broken relative link from schema.json to correct path
../../pkg/registry/data/schema.json in the registry schema documentation.

🤖 Generated with [Claude Code](https://claude.ai/code)

Signed-off-by: Daniele Martinoli <[email protected]>
Co-authored-by: Claude <[email protected]>

Author: dmartinol

docs/registry/schema.md

@@ -13,7 +13,7 @@ ToolHive MCP server registry and how to use it for validation and development.
 
 ## Overview
 
-The [`schema.json`](schema.json) file provides comprehensive validation for the
+The [`schema.json`](../../pkg/registry/data/schema.json) file provides comprehensive validation for the
 [`registry.json`](../../pkg/registry/data/registry.json) file structure. It
 ensures consistency, catches common errors, and serves as living documentation
 for contributors.