Fix codechecker complaints about PHPUnit naming

[abias]

Github actions started to complain recently about the naming of the existing PHPUnit tests:

FILE: ...r/work/moodle-availability_password/moodle-availability_password/moodle/availability/condition/password/tests/privacy_test.php
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FOUND 0 ERRORS AND 2 WARNINGS AFFECTING 1 LINE
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 36 | WARNING | PHPUnit testcase name "availability_password_privacy_test" does not match file name "privacy_test"
    |         | (moodle.PHPUnit.TestCaseNames.NoMatch)
 36 | WARNING | PHUnit class "availability_password_privacy_test" does not have any namespace. It is recommended to add it to the
    |         | "availability_password" namespace, using more levels if needed, in order to match the code being tested
    |         | (moodle.PHPUnit.TestCaseNames.MissingNS)
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This originates to a change in local_codechecker which was integrated there in moodlehq/moodle-local_codechecker#161

[abias]

This was solved recently in ed1535e