Remove Admin > Settings > Templates from sidenav when insufficient license

What does this MR do?

Issue #210456 (closed)

When the Templates feature is not included in the license, we should not be showing the link in the sidebar since it will lead to an empty page (because ee/app/views/admin/application_settings/_templates.html.haml is guarded by an if clause with the same condition). This MR removes the Admin > Settings > Templates link when a license does not include the custom_file_templates feature (currently GitLab Premium and above).

Screenshots

What the feature looks like (before)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability 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
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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