Explicitly set the status to be 204 for DELETE

We updated grape from 0.19.0 to 0.19.2, the diff is:

https://github.com/ruby-grape/grape/compare/v0.19.0...v0.19.2

This was introduced in grape 0.19.1:

* [#1550](https://github.com/ruby-grape/grape/pull/1550): Use 200 as default status for deletes that reply with content - [@jthornec](https://github.com/jthornec).

So now we need to be explicit about the status.

lib/api/ldap_group_links.rb

@@ -38,6 +38,7 @@ module API
         ldap_group_link = group.ldap_group_links.find_by(cn: params[:cn])
         if ldap_group_link
           ldap_group_link.destroy
+          status 204
         else
           render_api_error!('Linked LDAP group not found', 404)
         end
@@ -55,6 +56,7 @@ module API
         ldap_group_link = group.ldap_group_links.find_by(cn: params[:cn], provider: params[:provider])
         if ldap_group_link
           ldap_group_link.destroy
+          status 204
         else
           render_api_error!('Linked LDAP group not found', 404)
         end

lib/api/project_push_rule.rb

@@ -70,6 +70,7 @@ module API
         not_found!('Push Rule') unless push_rule
 
         push_rule.destroy
+        status 204
       end
     end
   end