Increase number of parallel ee:update jobs

Split ee:update jobs into 10 instead of 5. Recently, several ee:update jobs failed due to execution timeout (it went over 1 hour), e.g. https://ops.gitlab.net/gitlab-org/gitlab-qa/-/jobs/3678345. It is not surprising considering each job contains 60-70 tests to run and some are retried. Splitting them up across more jobs will help to prevent it and make the whole run faster.