[SCHEMA] Remove stale test comment -- test no longer fails!

[yarikoptic]

Test was written by @TheChymera awhile back. I didn't check if it was failing at that point but it is all nice and green now:

❯ python -m pytest -s -v bidsschematools/data/tests/test_rules.py::test_rule_objects
======================================== test session starts ========================================
platform linux -- Python 3.11.8, pytest-8.1.1, pluggy-1.4.0 -- /home/yoh/proj/bids/bids-specification/tools/schemacode/venvs/dev3/bin/python
cachedir: .pytest_cache
rootdir: /home/yoh/proj/bids/bids-specification/tools/schemacode
configfile: pyproject.toml
plugins: cov-4.1.0
collected 1 item                                                                                    

bidsschematools/data/tests/test_rules.py::test_rule_objects PASSED

on master (does fail on #1705)