remove the migration from Trieve docs and menu entry (#1013)

## Description

<!-- describe the changes as bullet points -->

- remove obsolete Trieve migration docs

## Testing Steps

- [x] Run the app locally using `fern docs dev` or navigate to preview deployment
- [x] Ensure that the changed pages and code snippets work

Author: cellog

fern/docs.yml

@@ -228,9 +228,6 @@ navigation:
                   - page: Custom knowledge base
                     path: knowledge-base/custom-knowledge-base.mdx
                     icon: fa-light fa-server
-                  - page: Migrating from Trieve
-                    path: knowledge-base/migrating-from-trieve.mdx
-                    icon: fa-light fa-triangle-exclamation
               - page: Argument encryption
                 path: tools/arguments-encryption.mdx
                 icon: fa-light fa-lock
@@ -1014,8 +1011,6 @@ redirects:
     destination: "/assistants/custom-tools"
   - source: "/knowledgebase"
     destination: "/knowledge-base"
-  - source: "/customization/bring-your-own-vectors/trieve"
-    destination: "/knowledge-base/integrating-with-trieve"
   - source: "/quickstart/billing"
     destination: "/billing/billing-faq"
   - source: /assistants/default-tools

fern/knowledge-base/custom-knowledge-base.mdx

@@ -529,7 +529,6 @@ app.post('/kb/search', async (req, res) => {
 Now that you have a custom knowledge base implementation:
 
 - **[Query Tool Configuration](/knowledge-base/using-query-tool):** Learn advanced query tool configurations
-- **[Vector Databases](/knowledge-base/integrating-with-trieve):** Explore vector database integrations
 - **[Assistant Configuration](/assistants):** Optimize your assistant's use of knowledge bases
 
 <Note>