Update CE specific specs to match CE version

What does this MR do?

The following specs don't match their versions in CE:

• spec/services/wiki_pages/create_service_spec.rb (CE version)
• spec/services/wiki_pages/destroy_service_spec.rb (CE version)
• spec/services/wiki_pages/update_service_spec.rb (CE version)

There's actually no difference in logic as they work the same way. But there's difference in how they were written.

EE behavior of the services are already tested in the corresponding specs under ee/ directory.

To ensure that there'll be no conflicts, the CE version of the said specs has been copy-pasted to overwrite the EE version.

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

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

Closes #6121 (closed)