Fix stacking order of emoji picker (#10801)

app/javascript/styles/mastodon/components.scss

@@ -3279,6 +3279,7 @@ a.status-card.compact:hover {
   box-shadow: 4px 4px 6px rgba($base-shadow-color, 0.4);
   border-radius: 4px;
   margin-top: 5px;
+  z-index: 2;
 
   .emoji-mart-scroll {
     transition: opacity 200ms ease;