Update requirements.txt

I was getting following error when installing this package on a GCP VM:
(myenv) (base) parallels@instance-2:~/DRL-GNN/DQN$ pip install --upgrade setuptools
Requirement already satisfied: setuptools in ./myenv/lib/python3.7/site-packages (67.6.1)
Collecting setuptools
  Using cached setuptools-67.7.2-py3-none-any.whl (1.1 MB)
Installing collected packages: setuptools
  Attempting uninstall: setuptools
    Found existing installation: setuptools 67.6.1
    Uninstalling setuptools-67.6.1:
      Successfully uninstalled setuptools-67.6.1
Successfully installed setuptools-67.7.2
(myenv) (base) parallels@instance-2:~/DRL-GNN/DQN$ pip install -r requirements.txt
Collecting absl-py==1.0.0 (from -r requirements.txt (line 1))
  Using cached absl_py-1.0.0-py3-none-any.whl (126 kB)
Collecting astunparse==1.6.3 (from -r requirements.txt (line 2))
  Using cached astunparse-1.6.3-py2.py3-none-any.whl (12 kB)
Collecting cachetools==4.2.4 (from -r requirements.txt (line 3))
  Using cached cachetools-4.2.4-py3-none-any.whl (10 kB)
Collecting certifi==2021.10.8 (from -r requirements.txt (line 4))
  Using cached certifi-2021.10.8-py2.py3-none-any.whl (149 kB)
Collecting charset-normalizer==2.0.7 (from -r requirements.txt (line 5))
  Using cached charset_normalizer-2.0.7-py3-none-any.whl (38 kB)
Collecting cloudpickle==2.0.0 (from -r requirements.txt (line 6))
  Using cached cloudpickle-2.0.0-py3-none-any.whl (25 kB)
Collecting cycler==0.11.0 (from -r requirements.txt (line 7))
  Using cached cycler-0.11.0-py3-none-any.whl (6.4 kB)
Collecting flatbuffers==2.0 (from -r requirements.txt (line 8))
  Using cached flatbuffers-2.0-py2.py3-none-any.whl (26 kB)
Collecting fonttools==4.28.1 (from -r requirements.txt (line 9))
  Using cached fonttools-4.28.1-py3-none-any.whl (873 kB)
Collecting gast==0.4.0 (from -r requirements.txt (line 10))
  Using cached gast-0.4.0-py3-none-any.whl (9.8 kB)
Collecting google-auth==2.3.3 (from -r requirements.txt (line 11))
  Using cached google_auth-2.3.3-py2.py3-none-any.whl (155 kB)
Collecting google-auth-oauthlib==0.4.6 (from -r requirements.txt (line 12))
  Using cached google_auth_oauthlib-0.4.6-py2.py3-none-any.whl (18 kB)
Collecting google-pasta==0.2.0 (from -r requirements.txt (line 13))
  Using cached google_pasta-0.2.0-py3-none-any.whl (57 kB)
Collecting grpcio==1.42.0 (from -r requirements.txt (line 14))
  Using cached grpcio-1.42.0-cp37-cp37m-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (4.0 MB)
Collecting gym==0.21.0 (from -r requirements.txt (line 15))
  Using cached gym-0.21.0.tar.gz (1.5 MB)
  Preparing metadata (setup.py) ... error
  error: subprocess-exited-with-error

  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [1 lines of output]
      error in gym setup command: 'extras_require' must be a dictionary whose values are strings or lists of strings containing valid project/version requirement specifiers.
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.
(myenv) (base) parallels@instance-2:~/DRL-GNN/DQN$
Slightly upgrading gym solved the issue for now (but upgrading it to the latest version requires more time to fix)
knowledgedefinednetworking / DRL-GNN

Update requirements.txt #17
