[BUG] Scipy 1.15 update causes failures in batched lbfgs pytest

[dantegd]

Updating SciPy to 1.15 causes the following (reproducible) unit test failure:

test_batched_lbfgs.py::test_batched_lbfgs_rosenbrock FAILED                                                                                                                                                                         [100%]

================================================================================================================ FAILURES =================================================================================================================
______________________________________________________________________________________________________ test_batched_lbfgs_rosenbrock ______________________________________________________________________________________________________
...
AssertionError: 
Not equal to tolerance rtol=1e-05, atol=0

Mismatched elements: 6 / 10 (60%)
Max absolute difference among violations: 0.16360418
Max relative difference among violations: 0.16822389
 ACTUAL: array([1.049671, 1.101809, 0.904425, 0.808934, 1.064853, 1.133886,
       1.151977, 1.327039, 0.976585, 0.953717])
 DESIRED: array([1.049671, 1.10181 , 0.986174, 0.972538, 1.064769, 1.133733,
       1.152303, 1.327802, 0.976585, 0.953718])

Marked it as xfail to unblock CI in #6207 while we look into it.