[TF] Remove TensorFlow derived conformances tests.

`TensorArrayProtocol` and `TensorGroup` have been [moved](tensorflow/swift-apis#139) to [tensorflow/swift-apis](https://github.com/tensorflow/swift-apis), and their derived conformances tests have been [copied](tensorflow/swift-apis#158) there as well. [tensorflow/swift-apis#165](tensorflow/swift-apis#165) changed the protocol requirements which made `TensorGroup` conformances no longer entirely derivable, but the derived conformances tests in this repo have not been updated, and it's blocking us from updating the checkout hash for tensorflow/swift-apis.

This PR removes `TensorGroup` derived conformance tests from apple/swift. We expect future changes to `TensorGroup` derived conformances to thoroughly test against tensorflow/swift-apis.

Author: rxwei