make a string not translatable

gajim/data/gui/add_new_contact_window.ui

@@ -127,7 +127,7 @@
             <property name="can_focus">True</property>
             <property name="hexpand">True</property>
             <property name="activates_default">True</property>
-            <property name="placeholder_text" translatable="yes">user@example.org</property>
+            <property name="placeholder_text">user@example.org</property>
           </object>
           <packing>
             <property name="left_attach">1</property>