lingo: remove unnecessary email placeholder in TIPI form (#15462)

combo/apps/lingo/templates/lingo/tipi_form.html

@@ -40,7 +40,7 @@
     </ul>
     <p>
       <label>{% trans "Email" %}</label>
-      <input type="email" id="mel" {% if request.user.email %}value="{{ request.user.email }}" {% endif %} placeholder="{% trans "user@example.net" %}" />
+      <input type="email" id="mel" {% if request.user.email %}value="{{ request.user.email }}" {% endif %} />
     </p>
     <p>
       <button>{% trans "Pay" %}</button>