Cannot add multiple instance-level kubernetes clusters on EE

Summary

Steps to reproduce

Add 1 instance-level cluster. The "add cluster" button will then be grayed out.

Example Project

https://autodevops.net/admin/clusters

What is the current bug behavior?

Only 1 cluster can be added

What is the expected correct behavior?

Admin should be able to add multiple clusters

Relevant logs and/or screenshots

Output of checks

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Results of GitLab environment info

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Results of GitLab application Check

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sudo gitlab-rake gitlab:check SANITIZE=true)
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(we will only investigate if the tests are passing)

Possible fixes

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