[#1743] Don't link to the deleted objects in "deleted" activities

The link would either be broken or to a page for a deleted object.

Old activities of other types ("created", "updated"...) will still link
to the deleted object if it has since been deleted.

ckan/templates/activity_streams/deleted_group.html

@@ -9,7 +9,7 @@
 ${activity_stream_activity(
   actor=h.linked_user(activity.user_id),
   verb='deleted',
-  object="the group "+h.group_link(activity.data.group),
+  object="the group "+activity.data.group.name,
   activity=activity
   )}
 </html>

ckan/templates/activity_streams/deleted_package.html

@@ -9,6 +9,6 @@
 ${activity_stream_activity(
   actor=h.linked_user(activity.user_id),
   verb='deleted',
-  object="the dataset "+h.dataset_link(activity.data.package),
+  object="the dataset "+h.dataset_display_name(activity.data.package),
   activity=activity)}
 </html>

ckan/templates/activity_streams/deleted_resource.html

@@ -9,8 +9,7 @@
 ${activity_stream_activity(
   actor=h.linked_user(activity.user_id),
   verb='deleted',
-  object='the resource '+h.resource_link(detail.data.resource,
-                                         activity.data.package.id),
+  object='the resource '+h.resource_display_name(detail.data.resource),
   target='from the dataset '+h.dataset_link(activity.data.package),
   activity=activity
   )}