Fixes #36395 - move value setting to seed

[ShimShtein]

No description provided.

[theforeman-bot]

Issues: #36395

[evgeni]

In #9500 we discussed that such things are better as seeds, not migrations.

[ShimShtein]

Moved to seeds

[evgeni]

I wonder if we should add a test for that in test/unit/tasks/seeds_test.rb? something like:

test 'ensures stable instance_id' do
  seed
  instance_id = Setting[:instance_id]
  assert instance_id, "instance_id was not generated"

  seed
  assert_equal instance_id, Setting[:instance_id]
end

[ShimShtein]

Tests added