Replaces inverted buttons with secondary buttons

`btn-confirm btn-inverted` => `btn-confirm-secondary`

app/views/projects/pipeline_schedules/_form.html.haml

@@ -27,7 +27,7 @@
           = render 'ci/variables/variable_row', form_field: 'schedule', variable: variable, only_key_value: true
         = render 'ci/variables/variable_row', form_field: 'schedule', only_key_value: true
       - if @schedule.variables.size > 0
-        %button.gl-button.btn.btn-confirm.btn-inverted.gl-mt-3.js-secret-value-reveal-button{ type: 'button', data: { secret_reveal_status: "#{@schedule.variables.size == 0}" } }
+        %button.gl-button.btn.btn-confirm-secondary.gl-mt-3.js-secret-value-reveal-button{ type: 'button', data: { secret_reveal_status: "#{@schedule.variables.size == 0}" } }
           - if @schedule.variables.size == 0
             = n_('Hide value', 'Hide values', @schedule.variables.size)
           - else