[FIX] digest: display unsubscribe even if no preferences to display

A wrongly-placed t-if prevented from displaying unsubscribe link (and the
"Sent by Odoo" sentence by the way, even if less annoying).

Task-2582128 (Digest onboarding and usage improvement)

X-original-commit: 669209b4
Part-of: odoo/odoo#79877

addons/digest/data/digest_data.xml

@@ -391,10 +391,11 @@
     </div>
 </div>
 
-<div t-if="preferences">
+<div>
     <div class="global_layout">
         <div class="preference_div">
-            <div t-foreach="preferences" t-as="preference" class="preference">
+            <div t-if="preferences" t-foreach="preferences" t-as="preference"
+                class="preference">
                 <t t-out="preference"/>
             </div>
             <div class="by_odoo">