fix: supabase_admin user for self-hosted read/write queries (supabase#39946)

Author: mattrossman

apps/studio/lib/api/self-hosted/constants.ts

@@ -5,5 +5,5 @@ export const POSTGRES_PORT = process.env.POSTGRES_PORT || 5432
 export const POSTGRES_HOST = process.env.POSTGRES_HOST || 'db'
 export const POSTGRES_DATABASE = process.env.POSTGRES_DB || 'postgres'
 export const POSTGRES_PASSWORD = process.env.POSTGRES_PASSWORD || 'postgres'
-export const POSTGRES_USER_READ_WRITE = 'postgres'
+export const POSTGRES_USER_READ_WRITE = 'supabase_admin'
 export const POSTGRES_USER_READ_ONLY = 'supabase_read_only_user'