fix(slider): use primary color for active dot border

Same fix as the thumb — use var(--ty-color-primary) so active dots
follow runtime theme changes.

Author: wangdicoder

components/slider/style/_index.scss

@@ -132,7 +132,7 @@
     transform: translate(-50%, -50%);
 
     &_active {
-      border-color: var(--ty-slider-dot-active-border);
+      border-color: var(--ty-color-primary);
     }
   }