[IMP] account: improve reconciliation congratulation message

If there was only one reconciliation the (rounded) time per transaction
was often different from the real one.

addons/account/static/src/xml/account_reconciliation.xml

@@ -52,7 +52,11 @@
 
 <div t-name="reconciliation.done" class="done_message">
     <h2>Congrats, you're all done!</h2>
-    <p>You reconciled <strong><t t-esc="number"/></strong> transactions in <strong><t t-esc="duration"/></strong>.<br/>That's on average <t t-esc="timePerTransaction"/> seconds per transaction.</p>
+    <p>You reconciled <strong><t t-esc="number"/></strong> transactions in <strong><t t-esc="duration"/></strong>.
+        <t t-if="number > 1">
+            <br/>That's on average <t t-esc="timePerTransaction"/> seconds per transaction.
+        </t>
+    </p>
     <t t-if="context &amp;&amp; context.active_model">
         <p t-if="context['active_model'] === 'account.journal' || context['active_model'] === 'account.bank.statement'" class="actions_buttons">
             <t t-if="context.journal_id">