Replace hint destination add_remove_clusters with add_eks_clusters

What does this MR do?

This MR changes hint that is visible on new EKS cluster page (k8s integration).

Old location (doesn't exist anymore): https://docs.gitlab.com/ee/user/project/clusters/add_remove_clusters.html#new-eks-cluster

New location: https://docs.gitlab.com/ee/user/project/clusters/add_eks_clusters.html#new-eks-cluster

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because it's a trivial change.
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

Virtually no risk. If I messed up, doc link won't work, so nothing broken in the product.

• [-] 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