ci: increase the files checked for changes before load docs cache

[germa89]

Description

Increase the files checked for changes before load docs cache.
Currently CICD does not check changes in the doc directory. This checks against it.

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)

[ansys-reviewer-bot]

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[germa89]

@pyansys-ci-bot LGTM.

[jorgepiloto]

✅ Approving this PR because germa89 said so in here 😬

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.21%. Comparing base (cda716a) to head (d413d75).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3237      +/-   ##
==========================================
- Coverage   82.64%   80.21%   -2.44%     
==========================================
  Files          53       53              
  Lines        9625     9625              
==========================================
- Hits         7955     7721     -234     
- Misses       1670     1904     +234