CHORE: Delete flaky tests

[Samuelopez-ansys]

Description

This pull request removes all infrastructure and code related to "flaky" tests on Linux, simplifying the test suite and CI/CD pipelines. The main changes include deleting the flaky_linux test marker, eliminating the corresponding test jobs from workflow files, and cleaning up all usages of the marker in test files.

Issue linked

Please mention the issue number or describe the problem this pull request addresses.

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).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.78%. Comparing base (e793cda) to head (9dcb480).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7068      +/-   ##
==========================================
- Coverage   83.50%   81.78%   -1.73%     
==========================================
  Files         254      254              
  Lines       77317    77317              
==========================================
- Hits        64567    63234    -1333     
- Misses      12750    14083    +1333     

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[SMoraisAnsys]

LGTM, please update the PR description

[eblanco-ansys]

LGTM

[MaxJPRey]

LGTM.