fix: increase n_trials from 5 to 10 in basic Optuna settings

Author: SvenKlaassen

doubleml/tests/_utils_tune_optuna.py

@@ -4,7 +4,7 @@
 
 def _basic_optuna_settings(additional=None):
     base_settings = {
-        "n_trials": 5,
+        "n_trials": 10,
         "sampler": optuna.samplers.TPESampler(seed=3141),
         "verbosity": optuna.logging.WARNING,
         "show_progress_bar": False,