Fix timestamp precision comparison in test

As https://gitlab.com/gitlab-org/gitlab/-/jobs/2232305277 shows:

```
 1) Ci::DeletedObject.bulk_import with data imports data
     Failure/Error: expect(deleted_artifact.pick_up_at).to eq(artifact.expire_at)
       expected: 2022-03-21 03:27:00.958060501 +0000
            got: 2022-03-21 03:27:00.958060000 +0000
       (compared using ==)
       Diff:
       @@ -1 +1 @@
       -Mon, 21 Mar 2022 03:27:00.958060501 UTC +00:00
       +Mon, 21 Mar 2022 03:27:00.958060000 UTC +00:00
```

spec/models/ci/deleted_object_spec.rb

@@ -22,7 +22,7 @@ RSpec.describe Ci::DeletedObject, :aggregate_failures do
         expect(deleted_artifact.file_store).to eq(artifact.file_store)
         expect(deleted_artifact.store_dir).to eq(artifact.file.store_dir.to_s)
         expect(deleted_artifact.file_identifier).to eq(artifact.file_identifier)
-        expect(deleted_artifact.pick_up_at).to eq(artifact.expire_at)
+        expect(deleted_artifact.pick_up_at).to be_like_time(artifact.expire_at)
       end
     end