Fix reassigned MR email

Former-commit-id: dd7c69da

app/views/notify/_reassigned_issuable_email.html.haml

-%p
-  Assignee changed
-  - if @previous_assignee
-    from
-    %strong= @previous_assignee.name
-  to
-  - if issuable.assignee_id
-    %strong= issuable.assignee_name
-  - else
-    %strong Unassigned

app/views/notify/reassigned_merge_request_email.html.haml

-Reassigned Merge Request #{ @merge_request.iid }
-
-= url_for([@merge_request.project.namespace.becomes(Namespace), @merge_request.project, @merge_request, { only_path: false }])
-
-Assignee changed
-- if @previous_assignee
-  from #{@previous_assignee.name}
-to
-= @merge_request.assignee_id ? @merge_request.assignee_name : 'Unassigned'
+%p
+  Assignee changed
+  - if @previous_assignee
+    from
+    %strong= @previous_assignee.name
+  to
+  - if @merge_request.assignee_id
+    %strong= @merge_request.assignee_name
+  - else
+    %strong Unassigned