update css classes

Author: Budmin

app/views/case_contacts/form/details.html.erb

@@ -147,7 +147,7 @@
         <div data-casa-nested-form-target="target"></div>
 
         <button type="button"
-          class="btn btn-sm btn-link"
+          class="main-btn secondary-btn  btn-hover"
           data-case-contact-form-target="addTopicButton"
           data-action="casa-nested-form#addAndCreate">
           + Add Another Discussion Topic