[Autoplay] Update string from muted to mute

Update sound settings string from muted to mute as per spec.

BUG=865548

Change-Id: Ib4a349627966995fc8abca36d10937d194f145ae
Reviewed-on: https://chromium-review.googlesource.com/1156990Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582000}

chrome/app/settings_strings.grdp

@@ -2954,7 +2954,7 @@
     Block
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_BLOCK_SOUND" desc="Label for add muted sites in site settings.">
-    Muted
+    Mute
   </message>
   <message name="IDS_SETTINGS_SITE_SETTINGS_SESSION_ONLY" desc="Label for sites in site settings allowing cookies for the current session only.">
     Clear on exit