Fix broken datepicker specs

Noticed this one while working on #3000. This test wasn't actually being run because it was inside a `let` block. Not sure how it wasn't blowing up, but obviously failing changes to it didn't fail. Moved it out of the `let` once I noticed it.

Once I did that, it was failing because the `data` attributes apparently weren't being rendered properly. Escaped them to properly test the expectation.