Fix use of KuiButtons in Clone Modal.

[cjcenizal]

When changes to the Buttons (#11878) were introduced, it caused tests for the Clone Modal (#10925) to fail because we didn't update the Buttons used by the Clone Modal. This is probably because the PR for changing the Buttons was created before the Clone Modal was updated.

Here's what the failure looks like:

renders DashboardCloneModal

    expect(value).toMatchSnapshot()
    
    Received value does not match stored snapshot 1.
    
    - Snapshot
    + Received
    
    @@ -35,24 +35,26 @@
         </div>
         <div
           class="kuiModalFooter"
         >
           <button
    -        class="kuiButton kuiButton--hollow"
    +        class="kuiButton"
             data-test-subj="cloneCancelButton"
    +        type="hollow"
           >
             <span
               class="kuiButton__inner"
             >
               <span>
                 Cancel
               </span>
             </span>
           </button>
           <button
    -        class="kuiButton kuiButton--primary"
    +        class="kuiButton"
             data-test-subj="cloneConfirmButton"
    +        type="primary"
           >
             <span
               class="kuiButton__inner"
             >
               <span>

[spalger]

LGTM, merged this into #12051 so we can get tests passing again

[spalger]

5.x: 8bb0776