fix(docs): use filters param for search in LiveKit integration

[kartik-mem0]

Description

The LiveKit integration docs use user_id=RAG_USER_ID as a direct kwarg in the search() call. However, the v2 search API (/v2/memories/search/) requires user_id inside the filters object it's a required field per the MemorySearchInputV2 schema in openapi.json.

With the current code, user_id gets placed at the top level of the payload where the API ignores it, so search silently returns empty results. Users following this guide get a voice agent with no memory recall.

Changed to filters={"user_id": RAG_USER_ID} which matches the v2 API contract and the official code samples.

Fixes #3832

Type of change

• Documentation update

How Has This Been Tested?

• Verified the MemorySearchInputV2 schema in openapi.json requires filters as a top-level field with user_id nested inside
• Traced the SDK code path in mem0/client/main.py:252-277 — confirmed user_id= kwarg lands at payload top level, not inside filters
• Confirmed the add() call using user_id= directly is correct (v1 endpoint accepts it at top level)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have checked my code and corrected any misspellings