Bug 1557579 - Fix autoplay permission label r=johannh,flod

Differential Revision: https://phabricator.services.mozilla.com/D35283

--HG--
extra : moz-landing-system : lando

browser/locales/en-US/chrome/browser/sitePermissions.properties

@@ -32,7 +32,7 @@ state.multichoice.autoplayblock = Block Audio
 state.multichoice.autoplayblockall = Block Audio and Video
 state.multichoice.autoplayallow = Allow Audio and Video
 
-permission.autoplay-media2.label = Autoplay sound
+permission.autoplay.label = Autoplay
 permission.cookie.label = Set Cookies
 permission.desktop-notification3.label = Send Notifications
 permission.image.label = Load Images

browser/modules/SitePermissions.jsm

@@ -888,7 +888,7 @@ var gPermissionObject = {
       }
       Services.prefs.setIntPref("media.autoplay.default", prefValue);
     },
-    labelID: "autoplay-media2",
+    labelID: "autoplay",
     states: [
       SitePermissions.ALLOW,
       SitePermissions.BLOCK,