Stop ensuring namespace directories for new repos

What are the relevant issue numbers?

Resolving this issue required a Gitaly change as the RenameNamespace RPC was the only one that didn't create missing parent directories: gitaly!1090 (merged). This change was released in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/26026

Resolves: https://gitlab.com/gitlab-org/gitlab-ce/issues/58012

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [-] Documentation created/updated via this MR
• [-] Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• [-] Tested in all supported browsers
• [-] Conforms to the code review guidelines
• [-] Conforms to the merge request performance guidelines
• [-] Conforms to the style guides
• [-] Conforms to the database guides
• [-] Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• [-] Security reports checked/validated by reviewer