Fix quota reset before next release

Today we hit problem of 1th of month where quota was not reset due to SQL timeout.

The problem is with this query: https://gitlab.com/gitlab-org/gitlab-ee/blob/master/app/workers/clear_shared_runners_minutes_worker.rb#L10.

We have:

> ProjectStatistics.count
=> 2385330

This leads to SQL query timeout. Thus we do not reset quotas. And process even that retried do fail.

The simplest fix is to change the offending code:

    ProjectStatistics.where('shared_runners_seconds > 0').
      update_all(shared_runners_seconds: 0,
        shared_runners_seconds_last_reset: Time.now)

    NamespaceStatistics.where('shared_runners_seconds > 0').
      update_all(shared_runners_seconds: 0,
        shared_runners_seconds_last_reset: Time.now)

But this, we limit data set to a reasonable amount and we do not hit the timeout. However, this is still not ideal, as we should reduce the number of updates at a single time to some amount, like 1k-10k.