improve chart type dialog treeview width

Change-Id: I41a053f63db6bced24dd6586e2c347d286339c29
Reviewed-on: https://gerrit.libreoffice.org/64076
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

chart2/uiconfig/ui/tp_ChartType.ui

@@ -406,6 +406,7 @@
                 <property name="visible">True</property>
                 <property name="can_focus">False</property>
                 <property name="vexpand">True</property>
+                <property name="hscrollbar_policy">never</property>
                 <property name="shadow_type">in</property>
                 <child>
                   <object class="GtkTreeView" id="charttype">