Regenerate name to avoid starting with underscore

[QRemy]

Prevent a random fail in the CI when auto-generated name start with underscore :
FAILED .....tox\py310-test-alldeps_noray\lib\site-packages\gammapy\visualization\tests\test_datasets.py::test_plot_spectrum_datasets_off_regions - matplotlib._api.deprecation.MatplotlibDeprecationWarning: An artist whose label starts with an underscore was passed to legend(); such artists will no longer be ignored in the future. To suppress this warning, explicitly filter out such artists, e.g. with [art for art in artists if not art.get_label().startswith('_')].

This should fix the break seen in #4759.

[codecov]

Codecov Report

Merging #4761 (662bd1c) into main (e53e1ea) will increase coverage by 0.02%.
Report is 11 commits behind head on main.
The diff coverage is 97.67%.

@@            Coverage Diff             @@
##             main    #4761      +/-   ##
==========================================
+ Coverage   76.02%   76.04%   +0.02%     
==========================================
  Files         223      223              
  Lines       32053    32085      +32     
==========================================
+ Hits        24367    24398      +31     
- Misses       7686     7687       +1     

Files Changed	Coverage Δ
gammapy/modeling/models/spectral.py	89.21% <96.87%> (+0.27%)	⬆️
gammapy/data/event_list.py	36.28% <100.00%> (-0.18%)	⬇️
gammapy/datasets/evaluator.py	89.72% <100.00%> (ø)
gammapy/modeling/models/spatial.py	85.02% <100.00%> (-0.03%)	⬇️
gammapy/modeling/models/tests/test_cube.py	91.52% <100.00%> (-0.02%)	⬇️
gammapy/modeling/models/tests/test_io.py	52.52% <100.00%> (+0.48%)	⬆️
gammapy/utils/scripts.py	89.13% <100.00%> (+0.49%)	⬆️

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[bkhelifi]

The CI fails because of ModuleNotFoundError: No module named 'astropy.coordinates.angle_utilities. But this is unrelated to this PR.

[bkhelifi]

Thanks @QRemy

[QRemy]

The CI fails because of ModuleNotFoundError: No module named 'astropy.coordinates.angle_utilities. But this is unrelated to this PR.

I tried to fix that direclty in this PR but I could open an other one instead.

[registerrier]

Thanks @QRemy. This looks good.

I think having the angular_utilities change in another PR would be better. But this can go as is.
This part of the PR can be backported too to ensure CI runs on bugfix branches with future versions.