Fix new clyngor

[cfrioux]

The latest version of clyngor leads to errors such as the following:

Traceback (most recent call last):
  File "/home/clemence/bin/miniconda3/envs/metage2metabo/lib/python3.8/site-packages/metage2metabo/m2m/individual_scope.py", line 144, in indiv_scope_on_species
    menescope_results = run_menescope(
  File "/home/clemence/bin/miniconda3/envs/metage2metabo/lib/python3.8/site-packages/menetools/menescope.py", line 66, in run_menescope
    model = query.get_scope(draftnet, seeds)
  File "/home/clemence/bin/miniconda3/envs/metage2metabo/lib/python3.8/site-packages/menetools/query.py", line 44, in get_scope
    for model in models.discard_quotes.by_arity:
  File "/home/clemence/bin/miniconda3/envs/metage2metabo/lib/python3.8/site-packages/clyngor/answers.py", line 205, in __iter__
    for answer_set, optimization, optimality, answer_number in self._answers:
  File "/home/clemence/bin/miniconda3/envs/metage2metabo/lib/python3.8/site-packages/clyngor/answers.py", line 327, in __compute_answers
    with self._solver.solve(**kwargs) as models:
TypeError: solve() got an unexpected keyword argument 'async'

This branch fixes the error by preventing the use of clingo module when calling the solver.