Remove stale xfail decorator from Newton environment tests (#5692)

Removed the stale file-level `@pytest.mark.xfail` decorator on
`test_environments_newton` (the cited Hydra deep nesting issue was
already resolved by PR #5029 and follow-ups #5130 / #5177).

## Checklist

- [x] I have read and understood the [contribution
guidelines](https://isaac-sim.github.io/IsaacLab/main/source/refs/contributing.html)
- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

Author: nvsekkin

source/isaaclab_tasks/changelog.d/esekkin-pr-a-newton-xfail.rst

@@ -0,0 +1,6 @@
+Fixed
+^^^^^
+
+* Removed the stale file-level ``@pytest.mark.xfail`` decorator on
+  ``test_environments_newton`` (the cited Hydra deep-nesting issue was already
+  resolved by PR #5029 and follow-ups #5130 / #5177).

source/isaaclab_tasks/test/test_environments_newton.py

@@ -36,14 +36,6 @@
     ),
 )
 @pytest.mark.newton_ci
-@pytest.mark.xfail(
-    reason=(
-        "TODO: Nested PresetCfg resolution for named presets (e.g. 'newton_mjwarp') is not yet supported. "
-        "The logic in parse_cfg.apply_named_preset should be unified with the deep-nesting "
-        "fixes in https://github.com/isaac-sim/IsaacLab/pull/5029 (isaaclab_tasks.utils.hydra)."
-    ),
-    strict=False,
-)
 def test_environments_newton(task_name, num_envs, device):
     # run environments with MJWarp physics preset
     _run_environments(task_name, device, num_envs, physics_preset_name="newton_mjwarp", create_stage_in_memory=False)