pyvista notebook build with sphinx gallery on CI

• Concern : API
• Platform : macOS/Linux/Windows
• Problem Description : When building the documentation using the gitlab CI pipeline, 3D exemples needs to be excluded from processing during the build otherwise an error of 'Kernel died' appears. This might be because pyvista plot (even in notebook mode?) need a display (which they don't when running the notebook from command line). There are various workaround on the web that include simulating a virtual display. However, as this issue doesn't impact our ability to run the notebook with pyvista on Binder, it's easier to run the notebook locally and exclude them from the CI (they usually take longer as well as 3D).
• How to reproduce it : modify dont_preprocess in doc/conf.py and then push to stable branch to run the pages job. The build will failed.