improved readability

app/vkk/templates/vkk/workhours/accounting/period/projects.html

@@ -36,7 +36,7 @@
             <td>{{ project.invoice_number }}</td>
             <td>{{ project.name }}</td>
             <td><a href="{% url 'vkk:workhours:accounting:projects:project:export:overview' project.invoice_number %}">{% translate "Export" %}</a></td>
-            <td style="text-align: center;">{% if project.exists_receipt %}☺️{% endif %}</td>
+            <td style="text-align: center;">{% if project.exists_receipt %}✅{% else %}❌{% endif %}</td>
         </tr>
     {% endfor %}
     </tbody>