Move jira_vulnerabilities_integration feature to Ultimate

What does this MR do?

Related to #289810 (comment 480807161)

This change moves Move jira_vulnerabilities_integration to GitLab Ultimate. We were not using jira_vulnerabilities_integration yet, it was not available for the end user and was hidden behind feature flag (jira_for_vulnerabilities). During the development process we have clarified that this should be an Ultimate feature.

The feature was not visible to the end user, because frontend is not yet ready and everything is put behind feature flag anyway, this makes it a safe change to do, because it will not affect anyone.

Changelog is not needed, since the feature was hidden behind feature flag.

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