Split ee:praefect job into 10 parallel

Several ee:praefect jobs failed this week due to execution timeout (1 hr) mostly due to the large number of tests and retries. For example - https://ops.gitlab.net/gitlab-org/gitlab-qa/-/jobs/4940044. To prevent jobs running over time limit and decrease the overall pipeline duration, this MR increases the amount of parallel jobs from 5 to 10.