Fix dialog close button (#16219)

* Fix dialog close button being white on almost white

* Make dialog close button slightly bigger

app/javascript/styles/mastodon/components.scss

@@ -5297,9 +5297,10 @@ a.status-card.compact:hover {
 .report-modal__target {
   padding: 15px;
 
-  .media-modal__close {
-    top: 14px;
-    right: 15px;
+  .report-modal__close {
+    position: absolute;
+    top: 10px;
+    right: 10px;
   }
 }