[DOC] remove single occurence from docs.py

[Remi-Gau]

Closes #3832

Changes proposed in this pull request:

• remove parameters definitions that were put in _utils.docs.py even though they are used only once in the whole code base.

[github-actions]

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[codecov]

Codecov Report

Merging #3834 (4486bd1) into main (8c62868) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #3834      +/-   ##
==========================================
- Coverage   91.54%   91.53%   -0.01%     
==========================================
  Files         133      133              
  Lines       15629    15623       -6     
  Branches     3250     3250              
==========================================
- Hits        14307    14301       -6     
  Misses        774      774              
  Partials      548      548              

Flag	Coverage Δ
macos-latest_3.10	91.46% <ø> (-0.01%)	⬇️
macos-latest_3.11	91.46% <ø> (-0.01%)	⬇️
macos-latest_3.8	91.42% <ø> (-0.01%)	⬇️
macos-latest_3.9	91.42% <ø> (-0.01%)	⬇️
ubuntu-latest_3.10	91.46% <ø> (-0.01%)	⬇️
ubuntu-latest_3.11	91.46% <ø> (-0.01%)	⬇️
ubuntu-latest_3.8	91.42% <ø> (-0.01%)	⬇️
ubuntu-latest_3.9	91.42% <ø> (-0.01%)	⬇️
windows-latest_3.10	91.40% <ø> (-0.01%)	⬇️
windows-latest_3.11	91.40% <ø> (-0.01%)	⬇️
windows-latest_3.8	91.36% <ø> (-0.01%)	⬇️
windows-latest_3.9	91.36% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
nilearn/_utils/docs.py	91.80% <ø> (-0.39%)	⬇️
nilearn/plotting/html_surface.py	100.00% <ø> (ø)
nilearn/plotting/img_plotting.py	89.66% <ø> (ø)
nilearn/plotting/surf_plotting.py	95.87% <ø> (ø)
nilearn/regions/parcellations.py	98.19% <ø> (ø)
nilearn/regions/rena_clustering.py	94.93% <ø> (ø)
nilearn/signal.py	97.15% <ø> (ø)

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[bthirion]

LGTM too.