match a expected value with message of assert_equal in AJ helper methods

[y-yagi]

In assert_equal calling in assert_enqueued_jobs and assert_performed_jobs, appoint the value that added original count and number to. However, appoint only number in error message.

Therefore, when call perform_later before calling assert_enqueued_jobs, output is different from Expected in error message.

test "sample1" do 
  GuestsCleanupJob.perform_later('guest 1')
  assert_enqueued_jobs 2 do
    GuestsCleanupJob.perform_later('guest 2')
  end
end

  1) Failure:
GuestsCleanupJobTest#test_test_1 [/home/yaginuma/program/rails/master/test/jobs/guests_cleanup_job_test.rb:6]:
2 jobs expected, but 1 were enqueued.
Expected: 3
  Actual: 2 

This patch fixes the argument of assert_equal, so it's output as follows.

  1) Failure:
GuestsCleanupJobTest#test_test_1 [/home/yaginuma/program/rails/master/test/jobs/guests_cleanup_job_test.rb:6]:
2 jobs expected, but 1 were enqueued.
Expected: 2
  Actual: 1

[senny]

@y-yagi good catch! 👍 I added a changelog entry and some test-cases in the merge commit 4d4950f

[y-yagi]

@senny Thanks!

[senny]

Backported to 4-2-stable: b081eda