fix(load-testing): remove duplicate createdUsers (#939)

The multiple-conversations scenario declared  twice, which caused the load-testing build to fail before any dependency PR could be evaluated meaningfully.

Verified with:
- cd services/load-testing && pnpm lint
- cd services/load-testing && pnpm build

Deploy: none

Author: nicobao

services/load-testing/src/scenario2-multiple-conversations.ts

@@ -151,11 +151,6 @@ const createdUsers: {
     prefixedKey: string;
 }[] = [];
 
-const createdUsers: {
-    did: string;
-    prefixedKey: string;
-}[] = [];
-
 // Backend DID from environment variable
 // Default to localhost for local development
 const BACKEND_DID = __ENV.BACKEND_DID || "did:web:localhost%3A8084";