Restore deleted ee/browser_ui/5_package folder

What does this MR do?

Adds back qa/qa/specs/features/ee/browser_ui/5_package with .gitkeep in it. The folder was removed in !36667 (merged) when all the tests were moved to Core part. As a result, the corresponding pipeline started failing - see https://ops.gitlab.net/gitlab-org/quality/production/-/jobs/1486155

Also removes .gitkeep from qa/qa/specs/features/browser_ui/5_package that now contains the tests and no longer empty.

Closes #231277 (closed)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content