Add an xfail for newer JAX versions that change sampler size behavior

tests/link/test_jax.py

@@ -1207,6 +1207,10 @@ def test_extra_ops_omni():
     compare_jax_and_py(fgraph, [])
 
 
+@pytest.mark.xfail(
+    version_parse(jax.__version__) >= version_parse("0.2.26"),
+    reason="JAX samplers require concrete/static shape values?",
+)
 @pytest.mark.parametrize(
     "at_dist, dist_params, rng, size",
     [