Maybe it can run faster when enqueue recurrring jobs?

File: Server/RecurringJobScheduler.cs
Method: EnqueueNextRecurringJobs

After:
```
var tasks = recurringJobIds.Select(recurringJobId => Task.Run(() =>
{
if (context.IsStopping) return false;

TryEnqueueBackgroundJob(context, connection, recurringJobId, now);
return true;
})).ToArray();
Task.WaitAll(tasks);
jobsProcessed = tasks.Count(x => x.Result);
```
Before:
```
// foreach (var recurringJobId in recurringJobIds)
// {
// if (context.IsStopping) break;
//
// TryEnqueueBackgroundJob(context, connection, recurringJobId, now);
// jobsProcessed++;
// }
```

**I want to run(enqueue) more recurring jobs and spend less time.**
This is a simple idea.