test(python): Fix version bifurcation for test_read_database_cx_credentials

[mcrumiller]

Closes #18218. Bifurcation occurs at 3.9.5, see the following for version evidence:

3.9.4

mcrumiller@Saline-PC:~/projects/polars/py-polars$ pyenv global 3.9.4
mcrumiller@Saline-PC:~/projects/polars/py-polars$ python
Python 3.9.4 (default, Aug 15 2024, 12:38:05) 
[GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import polars as pl
>>> uri = "fakedb://123:456@account/database/schema?warehouse=warehouse&role=role"
>>> pl.read_database_uri("SELECT * FROM data", uri=uri, engine="connectorx")
thread '<unnamed>' panicked at 'not implemented: Connection: fakedb://123:456@account/database/schema?warehouse=warehouse&role=role not supported!', /__w/connector-x/connector-x/connectorx/src/source_router.rs:80:18
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Traceback (most recent call last):
  File "/home/mcrumiller/projects/polars/py-polars/polars/io/database/_utils.py", line 54, in _read_sql_connectorx
    tbl = cx.read_sql(
  File "/home/mcrumiller/.pyenv/versions/3.9.4/lib/python3.9/site-packages/connectorx/__init__.py", line 257, in read_sql
    result = _read_sql(
pyo3_runtime.PanicException: not implemented: Connection: fakedb://123:456@account/database/schema?warehouse=warehouse&role=role not supported!

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/mcrumiller/projects/polars/py-polars/polars/io/database/functions.py", line 395, in read_database_uri
    return _read_sql_connectorx(
  File "/home/mcrumiller/projects/polars/py-polars/polars/io/database/_utils.py", line 66, in _read_sql_connectorx
    raise type(err)(errmsg) from err
pyo3_runtime.PanicException: not implemented: Connection: fakedb://***:***@account/database/schema?warehouse=warehouse&role=role not supported!

3.9.5

mcrumiller@Saline-PC:~/projects/polars/py-polars$ pyenv global 3.9.5
mcrumiller@Saline-PC:~/projects/polars/py-polars$ python
Python 3.9.5 (default, Aug 15 2024, 12:39:57) 
[GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import polars as pl
>>> uri = "fakedb://123:456@account/database/schema?warehouse=warehouse&role=role"
>>> pl.read_database_uri("SELECT * FROM data", uri=uri, engine="connectorx")
Traceback (most recent call last):
  File "/home/mcrumiller/projects/polars/py-polars/polars/io/database/_utils.py", line 54, in _read_sql_connectorx
    tbl = cx.read_sql(
  File "/home/mcrumiller/.pyenv/versions/3.9.5/lib/python3.9/site-packages/connectorx/__init__.py", line 386, in read_sql
    result = _read_sql(
RuntimeError: Source Unknown not supported.

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/mcrumiller/projects/polars/py-polars/polars/io/database/functions.py", line 395, in read_database_uri
    return _read_sql_connectorx(
  File "/home/mcrumiller/projects/polars/py-polars/polars/io/database/_utils.py", line 66, in _read_sql_connectorx
    raise type(err)(errmsg) from err
RuntimeError: Source Unknown not supported.

[alexander-beedie]

I imagine we did this to match CI rather than pinning down the exact minor version 😅
Nice work getting to the exact version!