RedisConcurrencyRateLimiter should use async Redis call to release the lease

[cristipufu]

https://github.com/dotnet/runtime/issues/77669

private void Release(ConcurencyLeaseContext leaseContext)
{
    var database = _connectionMultiplexer.GetDatabase();
    // how to use async? if only RateLimitLease would implement IAsyncDisposable
    database.SortedSetRemove($"rl:{_partitionKey}", leaseContext.RequestId);
}