[BUG] Testing skip not working properly for xdsl

[dime10]

Maybe someone can correct me here, but I don't think the pattern used here works as expected:

pennylane/tests/python_compiler/xdsl_extras/test_traits.py

Lines 24 to 27 in 54db80d

	xdsl = pytest.importorskip("xdsl")
	from xdsl.dialects.builtin import AnyAttr, TensorType, f32, i32, i64
	from xdsl.ir import Attribute

Even with the tests skipped, the module would still run the import statements and run into an error when xdsl is not installed.

I get the following when running pytest:

tests/python_compiler/xdsl_extras/test_traits.py:26: in <module>
    from xdsl.dialects.builtin import AnyAttr, TensorType, f32, i32, i64
E   ModuleNotFoundError: No module named 'xdsl.dialects'