Fix typo in UMA_INDEX_KNOWN_EXTENSIONS

Bug: None
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I4b0931917ec864739843a72d7de2dd430362db93
Reviewed-on: https://chromium-review.googlesource.com/952803Reviewed-by: Naoki Fukino <fukino@chromium.org>
Commit-Queue: Sasha Morrissey <sashab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541708}

ui/file_manager/file_manager/foreground/js/file_tasks.js

@@ -313,7 +313,7 @@ FileTasks.UMA_INDEX_KNOWN_EXTENSIONS = Object.freeze([
   '.wma',      '.wmv',         '.xls',
   '.xlsx',     '.crdownload',  '.crx',
   '.dmg',      '.exe',         '.html',
-  'htm',       '.jar',         '.ps',
+  '.htm',      '.jar',         '.ps',
   '.torrent',  '.txt',         '.zip',
   'directory', 'no extension', 'unknown extension',
   '.mhtml'