Mock error_tracking_setting to fix tests on failing master

What does this MR do?

Mocks error_tracking_setting helper method for tests.

Fixes failing master in https://gitlab.com/gitlab-org/gitlab-ce/issues/56052

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Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Tested in all supported browsers
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