[Dice] Change "Not syncing" string to "Sync is off"

When the user is signed in but not syncing, the title
in the user menu is changed to "Sync is off".

TBR=jochen@chromium.org

Bug: 900252
Change-Id: I29542e2c89fe381339ff8800a78c40a91092fe3d
Reviewed-on: https://chromium-review.googlesource.com/c/1310434Reviewed-by: Thomas Tangl <tangltom@chromium.org>
Commit-Queue: Thomas Tangl <tangltom@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604353}

chrome/app/profiles_strings.grdp

@@ -76,7 +76,7 @@
     Turn on sync...
   </message>
   <message name="IDS_PROFILES_DICE_NOT_SYNCING_TITLE" desc="Title of the sync promo account card in the user menu.">
-    Not syncing
+    Sync is off
   </message>
   <message name="IDS_PROFILES_DICE_SIGNIN_FIRST_ACCOUNT_BUTTON" desc="Button to sign in and turn on Sync for a specific web account.">
     Sync as <ph name="ACCOUNT_FULL_NAME">$1<ex>John Doe</ex></ph>