Fix sass warning about deprecated slash as division (#24653)

Co-authored-by: Nick Schonning <nschonni@gmail.com>

app/javascript/styles/mastodon/components.scss

@@ -1170,7 +1170,7 @@ body > [data-popper-placement] {
     width: 0;
     position: absolute;
     top: 0;
-    inset-inline-start: 16px + ((46px - 2px) / 2);
+    inset-inline-start: 16px + ((46px - 2px) * 0.5);
 
     &--full {
       top: 0;