Update internal link to use /index.md for consistency in IdentityServer documentation.

Author: khalidabuhakmeh

src/content/docs/identityserver/upgrades/identityserver4-to-duende-identityserver-v7.mdx

@@ -460,7 +460,7 @@ When upgrading, consider how those applications will handle an upgraded token se
 
 ### Step 7: Verify Data Protection Configuration :badge[Optional]
 
-Duende IdentityServer depends on [ASP.NET Data Protection](/identityserver/deployment/overview.md#aspnet-core-data-protection) to encrypt and sign data using keys managed by ASP.NET.
+Duende IdentityServer depends on [ASP.NET Data Protection](/identityserver/deployment/index.md#aspnet-core-data-protection) to encrypt and sign data using keys managed by ASP.NET.
 
 As part of your migration, verify the application name is set in your Data Protection configuration: