[QA] review all TODOs in test code

[nirajacharya2]

There are few TODOs in our test code instead of commenting on the code a issue should be created for it.

• TrashbinContext.php @S-Panta [tests-only]removed to do comment inside Trashbin #10424
• behat.yml [tests-only][full-ci]removed to do comment-in-behat-config #10434
• WebDav.php [QA] cleanup to-do in WebDav.php test code #10435
• WebDavHelper.php
• searchFederationUsers.feature -> Tracked in:Extend test coverage for ocm #10073