Update copyright to 2021

I know it seems like you just approved this but I found another
instance of the copyright.  It turns out we have 2, one for official
builds and another for unofficial builds.  AFAIK this is the last one
: )

Skip-Translation-Screenshots-Check: True
Change-Id: I80ad05d04facdb6e9c2ffe2126ba01b519b09681
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2628892
Commit-Queue: Joe Downing <joedow@chromium.org>
Commit-Queue: Jamie Walch <jamiewalch@chromium.org>
Auto-Submit: Joe Downing <joedow@chromium.org>
Reviewed-by: Jamie Walch <jamiewalch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843639}

remoting/resources/remoting_strings.grd

@@ -359,7 +359,7 @@
           The Chromium Authors
         </message>
         <message name="IDS_COPYRIGHT" desc="The copyright message specified in the version information of each Chromoting Host executable. It should be updated every year.">
-          Copyright 2013 The Chromium Authors. All Rights Reserved.
+          Copyright 2021 The Chromium Authors. All Rights Reserved.
         </message>
         <message name="IDS_DISPLAY_SERVICE_NAME" desc="The name of the Windows service installed by Chromoting.">
           Chromoting Service