Fix failing unit tests in Moodle 4.2

[golenkovm]

This is to resolve the following issues:

• PHP Deprecated: Calling reset() on an object is deprecated in php 8.1 #130
• Moodle 4.2 unit tests: Class "external_api" not found #140
• Moodle 4.2 unit tests: Class "report_customsql\external\get_users" not found #141

[timhunt]

I know you are trying to help, but this is not helpful. We ahve the test working wtih Moodle 4.2 in the OU code. We just have not pushed it to github yet because we have no time. We don't want to merge incompatible chagnes here.