Remove Duplicate Test

`should be able to be inserted...` occurs twice in the test file.
[ember-routing-htmlbars] Cleanup `ActionHelper`

DRY up `ActionHelper` cleanup in tests by moving to `teardown` block.
Include number of expected assertions

Without specifying the number of expected assertions, the callback might
never be evaluated, and the test might pass, acting as a false positive.
Merge pull request #9777 from seanpdoyle/ember-metal-bind-test-expectation

Include number of expected assertions
Merge pull request #9776 from seanpdoyle/teardown-action-helper

[ember-routing-htmlbars] Cleanup `ActionHelper`
Merge pull request #9775 from seanpdoyle/remove-duplicate-test

Remove Duplicate Test