Fix integration test for frost-table-header-selection

[job13er]

Somehow this default, non-frosty, non-functional test snuck through PR review:

https://github.com/ciena-frost/ember-frost-table/pull/13/files#diff-795138ec0941440443c7dd32bc24aaf5

It should be replaced by a real test.

[sglanzer-deprecated]

Totally my bad - wanted to get a team off my fork