Retire dead code

Unit tests live in `python/test/test_tc.py`.
The tests in `test_python/layers` are dead code at the moment since they
do not check output correctness and don't test any feature that isn't in
`python/test/test_tc.py` and they use the old API.
In the future, they can be revived in a single
`python/test/test_pytorch_layers.py` using the new API.

Author: nicolasvasilache