quick-add-popover.ui: propagate children height in calendar list

Due to changes in GTK+, scrolled windows do not propagate the natural
sizes of their children by default, which results in a tiny calendar
list.

https://bugzilla.gnome.org/show_bug.cgi?id=771401

data/ui/quick-add-popover.ui

@@ -208,6 +208,8 @@
                 <property name="hexpand">True</property>
                 <property name="vexpand">True</property>
                 <property name="shadow_type">in</property>
+                <property name="propagate-natural-height">True</property>
+                <property name="max-content-height">200</property>
                 <child>
                   <object class="GtkViewport">
                     <property name="visible">True</property>