Mark test_can_apply_ruff as xfail properly

This was a mistake in porting code to this repo.

Author: ryantam626

jupyterlab_code_formatter/tests/test_handlers.py

@@ -588,6 +588,7 @@ async def test_can_rustfmt(request_format):  # type: ignore[no-untyped-def]
     assert json_result["code"][0]["code"] == expected
 
 
+@pytest.mark.xfail(reason="Rust toolchain isn't respected in test for some reason atm.")
 async def test_can_apply_ruff(request_format):  # type: ignore[no-untyped-def]
     """Check that it can apply black with simple config."""
     response: HTTPResponse = await request_format(
@@ -600,5 +601,4 @@ async def test_can_apply_ruff(request_format):  # type: ignore[no-untyped-def]
         expected_code=200,
         expected_schema=EXPECTED_FROMAT_SCHEMA,
     )
-    import pdb; pdb.set_trace()
     assert json_result["code"][0]["code"] == "x = 22\ne = 1"