Move specs for Issues tabs to /ee/ folder

What does this MR do?

The specs for Issues tabs added in !16567 (merged) were added mistakenly outside of /ee/ folder.

The issues tabs only show up when the feature Design Management [EE] is enabled and allowed per license.

It's failing on gitlab-foss: https://gitlab.com/gitlab-org/gitlab-foss/-/jobs/307825005

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

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

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team