fix import style for redis.lock and luigi.task_register

[hirosassa]

Summary

• task_lock.py — Use from redis.lock import Lock instead of redis.lock.Lock attribute access
• build.py — Use from luigi import task_register instead of luigi.task_register attribute access

Motivation

Pyright does not resolve submodules via attribute chain access (e.g. redis.lock.Lock) unless the parent package explicitly re-exports them. Switching to direct imports follows the same pattern already used in parameter.py and resolves 6 Pyright errors.