improve active arrow and remove its px usage

frontend/src/routes/(frontend)/explore/layout.scss

@@ -12,9 +12,9 @@
     width: 0;
     height: 0;
     transform: translateX(-50%);
-    border-color: transparent transparent var(--wildebeest-color-400);
+    border-color: transparent transparent var(--wildebeest-color-500);
     border-style: solid;
-    border-width: 0 10px 10px;
+    border-width: 0 0.7rem 0.7rem;
     bottom: -1px;
   }