Replace success variant with the confirm

In the admin area, there is still deprecated button variant.
Updating it to the primary variant for consistency.

Changelog: fixed
EE: true

ee/app/views/shared/push_rules/_form.html.haml

@@ -61,4 +61,4 @@
   .form-text.text-muted
     = s_('PushRules|Reject file sizes equal to or greater than this size. If set to 0, files of any size are allowed. This rule does not apply to files tracked by Git LFS.')
 
-= f.submit s_("PushRules|Save push rules"), class: "btn gl-button btn-success", data: { qa_selector: 'submit_settings_button' }
+= f.submit s_("PushRules|Save push rules"), class: "btn gl-button btn-confirm", data: { qa_selector: 'submit_settings_button' }