style(tests): fix ruff format violation in TDD step file

Collapse multi-line @then decorator onto a single line in
tdd_session_create_suppress_exception_steps.py to satisfy
ruff format --check (the CI lint job runs both ruff check
and ruff format --check).

features/steps/tdd_session_create_suppress_exception_steps.py

@@ -114,9 +114,7 @@ class _CapturingHandler(logging.Handler):
         self.records.append(record)
 
 
-@then(
-    "a WARNING log entry should have been emitted for the facade dispatch failure"
-)
+@then("a WARNING log entry should have been emitted for the facade dispatch failure")
 def step_then_warning_logged(context: Context) -> None:
     """Assert that a WARNING log entry was emitted when the facade dispatch raised.