Dequarantine snippet tests

What does this MR do?

Dequarantines four snippet tests that are passing reliably on master now. The failures were only happening for praefect jobs, so to verify it on local you need to use the following command:

gitlab-qa Test::Integration::Praefect EE -- qa/specs/features/browser_ui/3_create/snippet --tag quarantine

See #298716 (closed) for more details.

NB there are different intermittent snippet failures on canary/production that are being investigated in #323852 (closed). They haven't been recorded on master so it shouldn't prevent this MR to go ahead. Moreover, if the tests will need to be quarantined in production, this will provide us with coverage in at least master.

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • [-] I have included a changelog entry.
  • I have not included a changelog entry because there is no change to application code.
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content