Hardcodes namespaces lease timing value to 1.5h

What does this MR do?

Hardcodes namespaces lease time value to 1.5h

After measuring the response and performance of the workers on https://gitlab.com/gitlab-org/gitlab-ce/issues/64092, we've decided 1.5 is fine for now. The time can be decreased later in the future when enforcing the quota limits

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• [-] 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

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers