docs: update image and code block

[germa89]

Description

While working on a presentation I saw this doc bugs I should fix

Issue linked

NA

Checklist

• I have visited and read Develop PyMAPDL.
• I have tested my changes locally
• I have added necessary documentation or updated existing documentation.
• I have followed the PyMAPDL coding style guidelines.
• I have added appropriate unit tests that also ensure the minimal coverage criteria.
• I have reviewed my changes before submitting this pull request.
• I have linked the issue or issues that are solved to the PR if any.
• I have assigned this PR to myself.
• I have marked this PR as draft if it is not ready to be reviewed yet.
• I have made sure that the title of my PR follows Commit naming conventions (e.g. feat: adding new MAPDL command)

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.82%. Comparing base (ad2d4dc) to head (93ef3a0).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3440      +/-   ##
==========================================
- Coverage   86.83%   86.82%   -0.02%     
==========================================
  Files          55       55              
  Lines        9975     9975              
==========================================
- Hits         8662     8661       -1     
- Misses       1313     1314       +1