Remove possible duplicate test XssUnitTest::testBadProtocolStripping

Problem/Motivation

While working on 📌 Fix class comment doc blocks in tests for 'Drupal.Commenting.DocComment.ShortSingleLine' Fixed I noticed that \Drupal\KernelTests\Core\Common\XssUnitTest appears to be duplicating tests that are elsewhere.

testBadProtocolStripping(). This is testing URL helper methods which are tested in \Drupal\Tests\Component\Utility\UrlHelperTest and with what appears to be more robust test data.

testT() - Surely t() has better testing elsewhere?

\Drupal\KernelTests\Core\Common\XssUnitTest was added in #1598564: Convert common.test to PSR-0 →

Steps to reproduce

Proposed resolution

Remove testBadProtocolStripping and possibly testT()

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet