[10.x] add getRedisConnection to ThrottleRequestsWithRedis

[snmatsui]

Problem

\Illuminate\Contracts\Redis\Factory usually become \Illuminate\Redis\RedisManager by DI.
DurationLimiter constructor expects \Illuminate\Redis\Connections\Connection, not \Illuminate\Contracts\Redis\Factory.
It now works because \Illuminate\Redis\RedisManager can behave as \Illuminate\Redis\Connections\Connection by using default connection.

Solution

Passing \Illuminate\Redis\Connections\Connection to DurationLimiter is more prefer.

Users who get benefits from this

Who wants to use Redis non-default connection for throttle count can override getRedisConnection method.