Creation of Brain object should not require curv.*h file

[Aaronearlerichardson]

Description of the problem

Plotting a pial brain surface should only require the pial surface files. This is evident in the mne freesurfer examples

Currently the initialization for the Brain object returns an error if missing a "curve.*h" file.

Steps to reproduce

from mne.viz import Brain

f = Brain(subject, subjects_dir=subjects_dir, cortex='low_contrast', alpha=0.5,
         background='grey', surf='pial')

Link to data

No response

Expected results

A plot of a brain

Actual results

File "C:\Users\ae166\git\SentenceRep_analysis\ieeg\viz\mri.py", line 312, in _
f = Brain(sub, subjects_dir=subj_dir, cortex='low_contrast', alpha=0.5,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\ae166.conda\envs\ieeg\Lib\site-packages\mne\viz_brain_brain.py", line 425, in init
geo.load_curvature()
File "C:\Users\ae166.conda\envs\ieeg\Lib\site-packages\mne\viz_brain\surface.py", line 179, in load_curvature
self.curv = read_curvature(curv_path, binary=False)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\ae166.conda\envs\ieeg\Lib\site-packages\mne\surface.py", line 815, in read_curvature
with open(filepath, "rb") as fobj:
^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: 'C:\Users\ae166\Box\ECoG_Recon\D28\surf\lh.curv

Additional information

Platform Windows-10-10.0.19044-SP0
Python 3.11.3 | packaged by Anaconda, Inc. | (main, Apr 19 2023, 23:46:34) [MSC v.1916 64 bit (AMD64)]
Executable C:\Users\ae166.conda\envs\ieeg\python.exe
CPU Intel64 Family 6 Model 158 Stepping 9, GenuineIntel (8 cores)
Memory 63.9 GB
Core
├☑ mne 1.4.0
├☑ numpy 1.24.3 (MKL 2023.1-Product with 4 threads)
├☑ scipy 1.10.1
├☑ matplotlib 3.7.1 (backend=TkAgg)
├☑ pooch 1.7.0
└☑ jinja2 3.1.2
Numerical (optional)
├☑ sklearn 1.2.2
├☑ numba 0.57.0
├☑ nibabel 5.1.0
├☑ dipy 1.7.0
├☑ pandas 2.0.1
└☐ unavailable nilearn, openmeeg, cupy
Visualization (optional)
├☑ pyvista 0.39.1 (OpenGL 4.5.0 - Build 30.0.101.1692 via Intel(R) HD Graphics 630)
├☑ pyvistaqt 0.10.0
├☑ vtk 9.2.6
├☑ qtpy 2.3.1 (PyQt5=5.15.2)
└☐ unavailable ipyvtklink, ipympl, pyqtgraph, mne-qt-browser
Ecosystem (optional)
├☑ mne-bids 0.12
└☐ unavailable mne-nirs, mne-features, mne-connectivity, mne-icalabel, mne-bids-pipeline