Breaking change in 1.16.5 due to removal of (deprecated) authentication.SymmetricKey

[maxrydkin]

This change removed SymmetricKey compatibility property from Device class.
Given, both property and the class have been marked as deprecated for a while, but feels like 1.16.4->1.16.5 is not the "major" release - so it affects users relying on semantic versioning.
In addition - if it is indeed being removed intentionally - maybe the test could also be cleaned up.