Ipyvtk_simple is not ipyvtk_link in 3D notebook viewer

Start with mne/viz/backends/_notebook.py and the plot_ecog.py example, then trace renderer.show() into PyVista’s notebook path. Reproduce with set_3d_backend("notebook") and verify that the backend handles the current ipyvtk package name and the example opens without ImportError.

Describe the bug

I am attempting to use the 3D backend notebook viewer for plotting an ecog brain. I get the following error:

---------------------------------------------------------------------------
ModuleNotFoundError                       Traceback (most recent call last)
~/Documents/sickkids/.venv/lib/python3.8/site-packages/pyvista/plotting/plotting.py in show(self, title, window_size, interactive, auto_close, interactive_update, full_screen, screenshot, return_img, cpos, use_ipyvtk, **kwargs)
   4323             try:
-> 4324                 from ipyvtk_simple.viewer import ViewInteractiveWidget
   4325             except ImportError:

ModuleNotFoundError: No module named 'ipyvtk_simple'

During handling of the above exception, another exception occurred:

ImportError                               Traceback (most recent call last)
<ipython-input-20-ea5cd7c5fb7d> in <module>
----> 1 fig = plot_alignment(
      2     raw.info,
      3     subject="E1",
      4     subjects_dir=subjects_dir,
      5     surfaces=["pial"],

<decorator-gen-151> in plot_alignment(info, trans, subject, subjects_dir, surfaces, coord_frame, meg, eeg, fwd, dig, ecog, src, mri_fiducials, bem, seeg, fnirs, show_axes, dbs, fig, interaction, verbose)

~/Documents/sickkids/.venv/lib/python3.8/site-packages/mne/viz/_3d.py in plot_alignment(***failed resolving arguments***)
   1098     renderer.set_camera(azimuth=90, elevation=90,
   1099                         distance=0.6, focalpoint=(0., 0., 0.))
-> 1100     renderer.show()
   1101     return renderer.scene()
   1102 

~/Documents/sickkids/.venv/lib/python3.8/site-packages/mne/viz/backends/_notebook.py in show(self)
    360         # viewer
    361         if LooseVersion(pyvista.__version__) < LooseVersion('0.30'):
--> 362             viewer = self.plotter.show(
    363                 use_ipyvtk=True, return_viewer=True)
    364         else:  # pyvista>=0.30.0

~/Documents/sickkids/.venv/lib/python3.8/site-packages/pyvista/plotting/plotting.py in show(self, title, window_size, interactive, auto_close, interactive_update, full_screen, screenshot, return_img, cpos, use_ipyvtk, **kwargs)
   4324                 from ipyvtk_simple.viewer import ViewInteractiveWidget
   4325             except ImportError:
-> 4326                 raise ImportError('Please install `ipyvtk_simple` to use this feature:'
   4327                                   '\thttps://github.com/Kitware/ipyvtk-simple')
   4328             # Have to leave the Plotter open for the widget to use

ImportError: Please install `ipyvtk_simple` to use this feature:	https://github.com/Kitware/ipyvtk-simple

However, this is because ipyvtk_simple is now named... ipyvtk-link :(

Steps to reproduce

Set mne.viz.set_3d_backend("notebook") and then run plot_ecog.py example.

Additional information

Platform:      macOS-10.16-x86_64-i386-64bit
Python:        3.8.6 | packaged by conda-forge | (default, Jan 25 2021, 23:22:12)  [Clang 11.0.1 ]
Executable:    /Users/adam2392/Documents/sickkids/.venv/bin/python
CPU:           i386: 8 cores
Memory:        Unavailable (requires "psutil" package)
mne:           0.24.dev0
numpy:         1.20.1 {blas=openblas, lapack=openblas}
scipy:         1.6.0
matplotlib:    3.3.4 {backend=agg}

sklearn:       0.24.1
numba:         0.52.0
nibabel:       3.2.1
nilearn:       Not found
dipy:          Not found
cupy:          Not found
pandas:        1.2.2
mayavi:        Not found
pyvista:       0.28.1 {pyvistaqt=0.4.0, OpenGL 4.1 ATI-4.4.17 via AMD Radeon Pro 560 OpenGL Engine}
vtk:           9.0.1
PyQt5:         5.15.2

Also ran w/ mne==0.23