Make monitor_gym configurable in WandbLogger. (#896)

At the moment, WandbLogger is always using wandb.init with monitor_gym =
True.
This fails when OpenAI's gym is not installed, which doesn't make sense
after the transition to Gymnasium.

I am using Tianshou with non-standard RL environment, which adhere to
Gymnasium API, and the current code is throwing exceptions.

I suggest to make it a controllable parameter. I left the default value
to True (to make it functionally the same for people using gym). It may
also make sense to change the default to False.

tianshou/utils/logger/wandb.py

@@ -54,6 +54,7 @@ class WandbLogger(BaseLogger):
         entity: Optional[str] = None,
         run_id: Optional[str] = None,
         config: Optional[argparse.Namespace] = None,
+        monitor_gym: bool = True,
     ) -> None:
         super().__init__(train_interval, test_interval, update_interval)
         self.last_save_step = -1
@@ -70,7 +71,7 @@ class WandbLogger(BaseLogger):
             resume="allow",
             entity=entity,
             sync_tensorboard=True,
-            monitor_gym=True,
+            monitor_gym=monitor_gym,
             config=config,  # type: ignore
         ) if not wandb.run else wandb.run
         self.wandb_run._label(repo="tianshou")  # type: ignore