Fix batch table toolbar displaying under status media (#35962)

app/javascript/styles/mastodon/tables.scss

@@ -195,7 +195,7 @@ a.table-action-link {
   &__toolbar {
     position: sticky;
     top: 0;
-    z-index: 1;
+    z-index: 200;
     border: 1px solid var(--background-border-color);
     background: var(--background-color);
     border-radius: 4px 4px 0 0;