Mark Qwen distribution tests as multi_device for CI collection

test_distribution and test_layout_map_mesh_shapes exercise real
DeviceMesh/ModelParallel sharding but were missing the multi_device
marker, so the dedicated CI job (-m "multi_device and not
kaggle_key_required and not extra_large") added in keras-team#2809 would
collect zero tests from this file.

For test_layout_map_mesh_shapes, the marker must go directly on the
function, below @parameterized.named_parameters(...): absl's
named_parameters expands each parameterization into a fresh bound
function via functools.wraps(test_method), which only carries over
attributes already present on the original function's __dict__, not
attributes attached afterward to the _ParameterizedTestIter wrapper
object that an outermost decorator would target. Placing the pytest
mark outermost silently drops it from every expanded test case.

test_layout_map_live_presets is already marked and intentionally
excluded by this job's own kaggle_key_required/extra_large filters,
so it is left untouched.

Author: pctablet505

keras_hub/src/models/qwen/qwen_backbone_test.py

@@ -171,6 +171,7 @@ def test_num_parameters(self):
         model = QwenBackbone(**self.init_kwargs)
         self.assertEqual(model.count_params(), 1384)
 
+    @pytest.mark.multi_device
     def test_distribution(self):
         self.run_distribution_test(
             cls=QwenBackbone,
@@ -206,6 +207,7 @@ def test_distribution(self):
         for dims in (QWEN_0_5B_DIMS, QWEN_3B_DIMS, QWEN_7B_DIMS)
         for shape in CAPPED_MESH_SHAPES
     )
+    @pytest.mark.multi_device
     def test_layout_map_mesh_shapes(self, dims, mesh_shape):
         if keras.backend.backend() != "jax":
             self.skipTest("`ModelParallel` testing requires the Jax backend.")