DOCS: Fix extension contribution code snippets

[SMoraisAnsys]

Description

Follow up of #6303, the code snippet were not rendering correctly.

Issue linked

Related to #6138

Checklist

• I have tested my changes locally.
• I have added necessary documentation or updated existing documentation.
• I have followed the coding style guidelines of this project.
• I have added appropriate tests (unit, integration, system).
• I have reviewed my changes before submitting this pull request.
• I have linked the issue or issues that are solved by the PR if any.
• I have agreed with the Contributor License Agreement (CLA).

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.37%. Comparing base (112373c) to head (7840cbd).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6384      +/-   ##
==========================================
- Coverage   85.37%   85.37%   -0.01%     
==========================================
  Files         175      175              
  Lines       66135    66137       +2     
==========================================
+ Hits        56464    56465       +1     
- Misses       9671     9672       +1     

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