Don't leave a key around when it doesn't have any values.
Revert "Bug 945222 - Update web-platform-tests expected data to revision e37ef9f403ddcdb50359adc8b9b2641a0ef3545b"

This reverts commit f54241bd7e33ee58ba2d8d41bb2506c0cc350651.
Bug 945222 - Update web-platform-tests expected data to revision e37ef9f403ddcdb50359adc8b9b2641a0ef3545b