`flatten_timepoint_specific_output_overrides` does not update visualization table

[dweindl]

flatten_timepoint_specific_output_overrides does not update the visualization table. The resulting problem does not pass validation. Can be observed, for example, with https://github.com/Benchmarking-Initiative/Benchmark-Models-PEtab/tree/v2024.10.15/Benchmark-Models/Isensee_JCB2018.

[m-philipps]

A flattened visualization table is probably not useful so the table could be removed for the flattened problem, as long as the visualization table stays optional.

[dweindl]

Agreed, unsetting problem.visualization_df would suffice. However, this should only happen if the changes really make the visualization table invalid.

[m-philipps]

fixed in #316