Add assertions ee_project_templates_spec.rb to narrow down possible template selection saving issue

What does this MR do?

Un-quarantines ee_project_templates_spec and adds assertion to ensure template selection is saved to pin point failure in https://gitlab.com/gitlab-org/gitlab-qa/-/jobs/252895191.

CE port: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/30835

Related issue: gitlab-org/quality/staging#61 (moved)

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