Remove legacy php-cs-fixer workflow

[berfinyuksel]

This PR removes the old php-cs-fixer GitHub Actions workflow file(s) from the repository, as they are now replaced by the reusable workflow.

Branch: phpcs_delete.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

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