[DOC] Fix wrong indentation of example code

[ymzayek]

• Closes None

Just a quick thing I noticed that the example here https://nilearn.github.io/stable/development.html#guidelines-for-private-functions doesn't have the right indentations

[Remi-Gau]

good with me

[github-actions]

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[codecov]

Codecov Report

Merging #4053 (96a0149) into main (b6f4ff0) will increase coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #4053      +/-   ##
==========================================
+ Coverage   91.48%   91.57%   +0.09%     
==========================================
  Files         143      143              
  Lines       16076    16076              
  Branches     3340     3340              
==========================================
+ Hits        14707    14722      +15     
+ Misses        823      807      -16     
- Partials      546      547       +1     

Flag	Coverage Δ
macos-latest_3.10	91.47% <ø> (ø)
macos-latest_3.11	91.47% <ø> (ø)
macos-latest_3.12	91.47% <ø> (ø)
macos-latest_3.8	91.43% <ø> (ø)
macos-latest_3.9	91.43% <ø> (ø)
ubuntu-latest_3.10	91.47% <ø> (ø)
ubuntu-latest_3.11	91.47% <ø> (ø)
ubuntu-latest_3.12	91.47% <ø> (ø)
ubuntu-latest_3.8	91.43% <ø> (ø)
ubuntu-latest_3.9	91.43% <ø> (ø)
windows-latest_3.10	91.41% <ø> (ø)
windows-latest_3.11	91.41% <ø> (?)
windows-latest_3.12	91.41% <ø> (ø)
windows-latest_3.8	91.37% <ø> (ø)
windows-latest_3.9	91.38% <ø> (ø)

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[bthirion]

LGTM, thx