tests: remove test_nested_marks (xfail)
tests: remove test_nested_marks (xfail)

It currently fails with a TypeError, and was not updated since 2013 -
therefore it can be assumed that it is not important to support it.

```
____________________ ERROR collecting test_nested_marks.py _____________________
…/Vcs/pluggy/src/pluggy/hooks.py:286: in __call__
    return self._hookexec(self, self.get_hookimpls(), kwargs)
…/Vcs/pluggy/src/pluggy/manager.py:93: in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
…/Vcs/pluggy/src/pluggy/manager.py:337: in traced_hookexec
    return outcome.get_result()
…/Vcs/pluggy/src/pluggy/manager.py:335: in <lambda>
    outcome = _Result.from_call(lambda: oldcall(hook, hook_impls, kwargs))
…/Vcs/pluggy/src/pluggy/manager.py:87: in <lambda>
    firstresult=hook.spec.opts.get("firstresult") if hook.spec else False,
…/Vcs/pytest/src/_pytest/python.py:235: in pytest_pycollect_makeitem
    res = list(collector._genfunctions(name, obj))
…/Vcs/pytest/src/_pytest/python.py:404: in _genfunctions
    self.ihook.pytest_generate_tests.call_extra(methods, dict(metafunc=metafunc))
…/Vcs/pluggy/src/pluggy/hooks.py:324: in call_extra
    return self(**kwargs)
…/Vcs/pluggy/src/pluggy/hooks.py:286: in __call__
    return self._hookexec(self, self.get_hookimpls(), kwargs)
…/Vcs/pluggy/src/pluggy/manager.py:93: in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
…/Vcs/pluggy/src/pluggy/manager.py:337: in traced_hookexec
    return outcome.get_result()
…/Vcs/pluggy/src/pluggy/manager.py:335: in <lambda>
    outcome = _Result.from_call(lambda: oldcall(hook, hook_impls, kwargs))
…/Vcs/pluggy/src/pluggy/manager.py:87: in <lambda>
    firstresult=hook.spec.opts.get("firstresult") if hook.spec else False,
…/Vcs/pytest/src/_pytest/python.py:130: in pytest_generate_tests
    metafunc.parametrize(*marker.args, **marker.kwargs)
…/Vcs/pytest/src/_pytest/python.py:965: in parametrize
    function_definition=self.definition,
…/Vcs/pytest/src/_pytest/mark/structures.py:111: in _for_parametrize
    if len(param.values) != len(argnames):
E   TypeError: object of type 'MarkDecorator' has no len()
!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!
```

Akasurde/pytest,The-Compiler/pytest,The-Compiler/pytest,RonnyPfannschmidt/pytest,nicoddemus/pytest,alfredodeza/pytest,nicoddemus/pytest,pytest-dev/pytest,markshao/pytest