Fix Study._log_completed_trial call

[c-bata]

I bumped a following exception while using kurobako-py@master with optuna@master.

Traceback (most recent call last):
  File "/home/runner/work/cmaes/cmaes/benchmark/optuna_solver.py", line 153, in <module>
    runner.run()
  File "/opt/hostedtoolcache/Python/3.10.4/x[64](https://github.com/CyberAgentAILab/cmaes/runs/5986187038?check_suite_focus=true#step:13:64)/lib/python3.10/site-packages/kurobako/solver/__init__.py", line 184, in run
    while self._run_once():
  File "/opt/hostedtoolcache/Python/3.10.4/x64/lib/python3.10/site-packages/kurobako/solver/__init__.py", line 200, in _run_once
    self._handle_tell_call(message)
  File "/opt/hostedtoolcache/Python/3.10.4/x64/lib/python3.10/site-packages/kurobako/solver/__init__.py", line 240, in _handle_tell_call
    solver.tell(trial)
  File "/opt/hostedtoolcache/Python/3.10.4/x64/lib/python3.10/site-packages/kurobako/solver/optuna.py", line 184, in tell
    self._study._log_completed_trial(trial, values)
TypeError: Study._log_completed_trial() takes 2 positional arguments but 3 were given

The parameters of Study._log_completed_trial() are changed at Optuna v3.0.0-b0 release. Please see optuna/optuna@6a6b0ab for details.

[sile]

Thanks!

I think that it might be better to define the logging logic within kurobako-py in the future to stop using Optuna's private methods. However, anyway, this PR itself seems nice!