Fix broken link to deleted quickstart.mdx

Update configuration.mdx to link to intro.mdx instead of the
deleted quickstart.mdx file.

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: JAORMX

docs/toolhive/guides-vmcp/configuration.mdx

@@ -160,6 +160,6 @@ spec:
 
 ## Related information
 
-- [Deploy Virtual MCP Server](./quickstart.mdx)
+- [Introduction to Virtual MCP](./intro.mdx)
 - [Tool aggregation](./tool-aggregation.mdx)
 - [Authentication](./authentication.mdx)