fix ruff

Author: m-philipps

petab/v1/core.py

@@ -303,7 +303,9 @@ def flatten_timepoint_specific_output_overrides(
     # remove visualization df if it is invalid
     if validate_visualization_df(petab_problem):
         petab_problem.visualization_df = None
-        logger.warning("Removing visualization table from flattened PEtab problem.")
+        logger.warning(
+            "Removing visualization table from flattened PEtab problem."
+        )
 
 
 def unflatten_simulation_df(