[Python] Fix PytestUnraisableExceptionWarning in substrait test

### Describe the bug, including details regarding any error messages, version, and platform.

[`test_named_table_invalid_table_name` ](https://github.com/apache/arrow/blob/63f013cdb36d05f6f96a145aff3c6232470f2d02/python/pyarrow/tests/test_substrait.py#L229) generates a `PytestUnraisableExceptionWarning` in the tests. The exception itself is:
> Traceback (most recent call last):
File "/home/joris/scipy/repos/arrow/python/pyarrow/tests/test_substrait.py", line 238, in table_provider
raise Exception("Unrecognized table name")
Exception: Unrecognized table name

The exception ought to be raised properly instead of 'hidden' as a warning.

### Component(s)

Python

Start with test_named_table_invalid_table_name in python/pyarrow/tests/test_substrait.py, especially the table_provider code around line 238, and reproduce the PytestUnraisableExceptionWarning. Done means the “Unrecognized table name” exception is raised properly by the test and the warning is no longer emitted.

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