HasLineLongerThanMaxTest: remove a `@covers` tag
HasLineLongerThanMaxTest: remove a `@covers` tag

As the `PHPMailer::encodeString()` method is now fully covered by dedicated tests, this `@covers` tag can be removed.

jimjag/PHPMailer,nawawi/PHPMailer,jimjag/PHPMailer,PHPMailer/PHPMailer,nawawi/PHPMailer,PHPMailer/PHPMailer