Fix security discovery carousel slider event value

It should use the property which accepts non numeric

ee/app/assets/javascripts/vue_shared/discover/card_security_discover_app.vue

@@ -77,7 +77,7 @@ export default {
     onSlideStart(slide) {
       this.track('click_button', {
         label: 'security-discover-carousel',
-        value: `sliding${this.slide}-${slide}`,
+        property: `sliding${this.slide}-${slide}`,
       });
       this.textSlide = slide;
     },

ee/spec/frontend/vue_shared/discover/card_security_discover_app_spec.js

@@ -78,6 +78,18 @@ describe('Card security discover app', () => {
         });
       });
 
+      it('tracks an event when clicked on a slider', () => {
+        const expectedCategory = undefined;
+
+        document.body.dataset.page = '_category_';
+        wrapper.vm.onSlideStart(1);
+
+        expect(spy).toHaveBeenCalledWith(expectedCategory, 'click_button', {
+          label: 'security-discover-carousel',
+          property: 'sliding0-1',
+        });
+      });
+
       it('tracks an event when clicked on feedback', () => {
         wrapper.find('.discover-feedback-icon').trigger('click');