feat(dot-net): Added redirects for deleted API docs

src/content/docs/agents/net-agent/getting-started/8x-to-9x-agent-migration-guide.mdx

@@ -5,6 +5,9 @@ tags:
   - NET agent
   - Migration guides
 metaDescription: 'This guide helps New Relic .NET agent users migrate from 8.x versions to 9.x'
+redirects:
+  - /docs/agents/net-agent/net-agent-api/addcustomparameter-net-agent-api
+  - /docs/agents/net-agent/net-agent-api/idistributedtracepayload-net-agent-api
 ---
 
 This guide outlines the major changes between the 8.x and 9.x versions of the .NET agent, issues that you may encounter while upgrading, and how to migrate successfully to version 9.x.