Files app: Fix FilesMetadataEntry variable name

This has been wrong since this file was created:
https://codereview.chromium.org/2109563002

Bug: 1029211
Change-Id: I9e95c0180ef31868a2dfe63a6f723f0d1eb9f422
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1941649
Auto-Submit: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719916}

ui/file_manager/file_manager/foreground/elements/files_metadata_entry.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-var FilesMetadataBox = Polymer({
+const FilesMetadataEntry = Polymer({
   is: 'files-metadata-entry',
 
   properties: {