CI/CD Pipeline is broken: fix code checker

[icaparros-at-wiris]

Description

The dependency moodle-plugin-ci that we use to test and analyze our Moodle suit projects code, has been updated to 3.2.3, introducing the following changes:

• PHP_CodeSniffer upgraded to 3.6.2 release (see: https://github.com/squizlabs/PHP_CodeSniffer/releases/tag/3.6.2)
• Report unexpected MOODLE_INTERNAL uses (see: https://github.com/moodlehq/moodle-local_codechecker/pull/169) This change affects directly to our GitHub Actions workflow, it makes it fail, hence it does not allow us to make new releases of the Moodle suite.

  Implementation

  The new release of the moodle-plugin-ci dependency claims that, all PHP files without side-effects must remove unnecessary MOODLE_INTERNAL requirements.

  defined('MOODLE_INTERNAL') || die();

  What is included on this PR:

  This PR also includes:

• Remove other warning and errors not related to the MOODLE_INTERNAL one.
• Updated CHANGELOG

  Steps to reproduce

• On the Actions tab, find the "Moodle Plugin CI" workflow.
• Use the workflow dispatch option on the KB-19424 branch.

• All moodle code checker verifications should pass without warnings or errors. Check GitHub Actions results

  #taskid 19424