Doc builds failing when using plotly

[Remi-Gau]

This seems to be a new thing:
https://github.com/nilearn/nilearn/actions/workflows/build-docs.yml?query=branch%3Amain

The build goes on for 6 hours and then is killed.

See here:
https://github.com/nilearn/nilearn/actions/runs/8642310331/job/23693214886#step:34:484

It seems to be related to plotting something with plotly:

nilearn/examples/01_plotting/plot_3d_map_to_surface_projection.py

Line 90 in 71e9f41

fig.show() # Display the figure as with matplotlib figures

Possibly related to:

• [BUG] plotly in nilearn.surface.vol_to_surf opens two interactive windows #4376
• flaky test_plotly_savefig time-out on GHA workflow for tests on windows  #3925