tdf#123013: Allow to change trendline name in gtk3

Change-Id: I3eeb6b8e27cced0a8a86969368f48a2af8ac5892
Reviewed-on: https://gerrit.libreoffice.org/67026
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

chart2/uiconfig/ui/tp_Trendline.ui

@@ -467,7 +467,7 @@
                 <child>
                   <object class="GtkEntry" id="entry_name">
                     <property name="visible">True</property>
-                    <property name="can_focus">False</property>
+                    <property name="can_focus">True</property>
                     <property name="activates_default">True</property>
                   </object>
                   <packing>