Remove unnecessary sign out statements in QA test

What does this MR do?

Removes sign out statements from a test. The before(:all) block now signs out, and Capybara resets the session after each test, so there's no need to sign out at the start of each test.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content