ray dependency not removed properly

[JinraeKim]

TL; DR
After installing fym in a newly created conda environment with Python 3.8:

(ftc-jiwon) ➜  fault-tolerant-control-jiwon git:(LC62-CA-Transition) ✗ python examples/allocator_l1.py
Traceback (most recent call last):
  File "examples/allocator_l1.py", line 3, in <module>
    from controller_lqr_LC62_Binary import MyEnv
  File "/Users/jinrae/workspace/ftc/fault-tolerant-control-jiwon/examples/controller_lqr_LC62_Binary.py", line 11, in <module>
    import fym
  File "/Users/jinrae/workspace/nrf/fym/fym/__init__.py", line 7, in <module>
    from .utils.ray import generate_variants
ModuleNotFoundError: No module named 'fym.utils.ray'

[seong-hun]

Resolved in aac00ff