Warnings raised by underlying `seaborn` and `numpy` libraries

[zzril]

Is your feature request related to a problem?

When running the test suite, currently 3 warnings will be raised from underlying libraries (seaborn and numpy) and are not catched.

These are the corresponding testcases:

• tests/safeds/data/tabular/containers/_table/test_plot_correlation_heatmap.py::test_should_match_snapshot[empty]
• tests/safeds/data/tabular/containers/_table/test_plot_correlation_heatmap.py::test_should_match_snapshot[empty]
• tests/safeds/data/tabular/containers/_table/test_plot_histograms.py::test_should_match_snapshot[four columns]

For the first 2, the warnings are raised by some seaborn module and seems to have the same cause, the 3rd one is some numpy thing.

Desired solution

Ideal solution: Find the cause of the warnings and change the code to not produce these warnings anymore.

Possible alternatives (optional)

If it's absolutely clear that we can't do anything to fix these warnings:
Silence them in the code that produced them. (Not just in the tests!)

[lars-reimann]

We should configure Pytest to treat all warnings as errors (unless specifically ignored) in pyproject.toml, as described here.

[lars-reimann]

How to ignore warnings: https://github.com/Safe-DS/Stdlib/blob/c5d75df0c6a548eafe9caef291f0360b28a1d548/src/safeds/data/tabular/containers/_table.py#L1932-L1937

[zzril]

Updated the description to state that we don't just want to silence the warnings in the tests, but in the code that throws them.