Files app: Remove unnecessary IF

The query and the remvoval are performed in-line, so checking for
"contains()" isn't necessary.

Bug: 1056443
Change-Id: I86a5dc0601948502b0ce0a94845422b4db07fd7f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2078515
Commit-Queue: Noel Gordon <noel@chromium.org>
Auto-Submit: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745290}

ui/file_manager/file_manager/foreground/js/ui/file_table.js

@@ -1147,9 +1147,7 @@ class FileTable extends cr.ui.Table {
     const oldThumbnails = box.querySelectorAll('.thumbnail');
 
     for (let i = 0; i < oldThumbnails.length; i++) {
-      if (box.contains(oldThumbnails[i])) {
-        box.removeChild(oldThumbnails[i]);
-      }
+      box.removeChild(oldThumbnails[i]);
     }
 
     box.appendChild(thumbnail);