Backport from h5p master

[ScottVerbeek]

Commit fb62787 contains the following h5p/h5p-php-library@fb62787#diff-89117fe225bccb930971b72569064b31f631ae2b7a717300b4cf2845fb14ec6eR4859-R4864 . This will cause a unit test failure in MDL39.

1) core_h5p\api_testcase::test_get_export_info_from_context_id
Unexpected debugging() call detected.
Debugging: String translation cannot be found. Please add a string definition for 'Assistive Technologies label' in the core_h5p component.

/var/www/site/lib/phpunit/classes/advanced_testcase.php:88

To re-run:
 vendor/bin/phpunit "core_h5p\api_testcase" h5p/tests/api_test.php

[ScottVerbeek]

Reverted commits made in Pull request #3