FIX: Fixes for Latest IPython (9.0.1)

[scott-huberty]

As seen in The failing ubuntu-latest job of #13145

FAILED mne/viz/backends/tests/test_abstract.py::test_widget_abstraction_notebook[notebook] - nbclient.exceptions.CellExecutionError: An error occurred while executing the following cell:
"""Test the GUI widgets abstraction in notebook."""
from pathlib import Path

from IPython import get_ipython

from mne.viz import set_3d_backend
from mne.viz.backends.renderer import _get_backend
from mne.viz.backends.tests.test_abstract import _do_widget_tests

set_3d_backend("notebook")
backend = _get_backend()
assert Path(backend.__file__).stem == "_notebook"

ipython = get_ipython()
ipython.magic("%matplotlib widget")
_do_widget_tests(backend)
------------------

----- stdout -----
Using notebook 3d backend.
------------------

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
Cell In[1], line 15
     12 assert Path(backend.__file__).stem == "_notebook"
     14 ipython = get_ipython()
---> 15 ipython.magic("%matplotlib widget")
     16 _do_widget_tests(backend)

AttributeError: 'ZMQInteractiveShell' object has no attribute 'magic'

From what I can gather, the .magic method is deprecated ( ref ), and this may be why test_widget_abstraction_notebook is failing with the latest IPython (9.0.1)

I can't replicate the CI failure locally on my Mac, but here I am replacing .magic with run_line_magic, which seems to be the recommended way? Opening this PR to see if it fixes it..

[larsoner]

LGTM +1 for merge once it comes back green