perf(backend): 通知をRedisに保存するように

Resolve #10168

packages/backend/src/di-symbols.ts

@@ -33,7 +33,6 @@ export const DI = {
 	emojisRepository: Symbol('emojisRepository'),
 	driveFilesRepository: Symbol('driveFilesRepository'),
 	driveFoldersRepository: Symbol('driveFoldersRepository'),
-	notificationsRepository: Symbol('notificationsRepository'),
 	metasRepository: Symbol('metasRepository'),
 	mutingsRepository: Symbol('mutingsRepository'),
 	renoteMutingsRepository: Symbol('renoteMutingsRepository'),